Re: [PSES] input current rating
Dear Bostjan: One of the uses of current rating on equipment is to determine that the equipment, with all of the other equipment, would not overload the mains circuit. If the actual current exceeds the marked current, then the equipment, with all of the other equipment, can overload the mains but there is no means to identify the culprit equipment. Note, however, that there is no limit on lower current than rated current. I suspect this is because much equipment has an idle mode during which the input current is minimum. Best regards, Rich - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas sdoug...@ieee.org Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] UL 60950-1 clause 2.2.3
HI John: As mentioned in my first response, you will have the same problem (half the mains on the enclosure) if you use a Class II power supply. If you talk with your NRTL, I'm sure he will accept your construction based on 60950-1, 5.1 rather than 60950-22. Your equipment is not unsafe with the ground open if it complies with 5.1. (And it will!) Best regards, Rich - Original Message - From: John Cochran jcoch...@strongarm.com Date: Monday, September 8, 2014 8:04 am Subject: Re: [PSES] UL 60950-1 clause 2.2.3 It appears that I can only meet this requirement for outdoor enclosures by either using a Class 2 power supply, or require the installer to use the external ground connection in addition to the internal PE ground. The system is safe under normal conditions, but only has hazardous voltages on the enclosure when the PE ground is broken. Are there any opposing opinions? John Cochran STRONGARM Designs 425 Caredean Drive Horsham, PA 19044 PHONE: 215-443-3400 X193 FAX: 215-443-3002 -Original Message- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Monday, September 08, 2014 2:42 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] UL 60950-1 clause 2.2.3 In message f6d1e59f218e.540c8...@bendbroadband.com, dated Sun, 7 Sep 2014, Rich Nute ri...@bendbroadband.com writes: I believe the authors of 60950-22 expected that user-accessible parts would comprise SELV circuits rather than grounded parts. See 2.1.1 and 2.2 in 60950-1. Grounded parts would be subject to 5.1 in 60950-1. Thank you. So what can the OP do? Does this need to be taken into account in a revision or replacement of 60950-22? -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Quid faciamus nisi sit? John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] UL 60950-1 clause 2.2.3
Hi John: I believe the authors of 60950-22 expected that user-accessible parts would comprise SELV circuits rather than grounded parts. See 2.1.1 and 2.2 in 60950-1. Grounded parts would be subject to 5.1 in 60950-1. Best regards, Rich - Original Message - From: John Cochran jcoch...@strongarm.com Date: Sunday, September 7, 2014 1:42 pm Subject: RE: [PSES] UL 60950-1 clause 2.2.3 Actually I need to meet the standard for outdoor enclosures, UL 60950-22, and clause 6.1 refers back to UL 60950-1 clause 2.2.2 and 2.2.3. The difference is the voltage limits are reduced, due to contact resistance of the body being reduced when subjected to wet locations. The clause states the voltage difference under a single fault must not exceed 30 V ac, without any mention of current. Am I reading this correctly? John Cochran STRONGARM Designs 425 Caredean Drive Horsham, PA 19044 PHONE: 215-443-3400 X193 FAX: 215-443-3002 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
RE: RF What-if (was: RE: Another Cancer Scare?)
Back in the old days -- say mid-50's or earlier, broadcast transmitters were required to be monitored full-time by a qualified engineer. High-power AM transmitters bombarded these guys with all kinds of stuff. Many of these old-timers reported effects on the brain, but I can't remember the details. But, they did survive to tell the tales! (For 25 years or so, I worked side-by-side with a former transmitter engineer.) Different frequency, different power, probably different effects on the human body. We still have public concerns that transmitter radiation at the periphery of the site is too much. Paul Brodeur's book, Currents of Death, (based on faulty research) popularized the notion of cancer from any transmitter as well as power transmission lines and video display terminals. Rich -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Chris Wells Sent: Wednesday, July 30, 2008 6:26 PM To: Oscar Overton Cc: emc-p...@ieee.org; k...@earthlink.net Subject: Re: RF What-if (was: RE: Another Cancer Scare?) Oscar - I spend a lot of time debugging systems and separating coincidence from cause so I appreciate your skeptic stance. I would agree that it was not a controlled experiment but it was my experience that I wanted to share. My exposure was over a good part of a month and my flu like symptoms happened at the exposure time and stopped ~ 4hrs+ later after leaving the area. I would estimate ~ 15 exposures events over that month and then many months before and after without any problems. As a result of my experience I am being cautious, limiting unnecessary exposure and since I work with power being observant of other situations. Chris Wells From: Oscar Overton oover...@lexmark.com Chris, Until you can do this repeatedly and the results are the same, you have only demonstrated a coincidence. Oscar Overton Product Safety - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: IEC 62368
Hi Brian: 1. What is the status of IEC62368 and the associated and infamous IEC62441 ? Ultimately, when are 60950-1 and 60065 projected to be replaced by 62368 ? CDV2 will be issued to National Committees for voting this or next month. (You can get a copy from your National Committee.) Voting will be complete in 5 months. If the vote is yes, then a FDIS will be issued. Regarding replacement of 60950-1 and 60065, the CDV2 states: The attention of National Committees and National bodies who prepare national standards is drawn to the fact that equipment manufacturers and testing organizations may need a transitional period following publication of a new, amended or revised IEC publication in which to make products in accordance with the new requirements and to equip themselves for conducting new or revised tests. It is the recommendation of TC108 that the content of this publication be adopted for mandatory implementation nationally not earlier than five years from the date of publication of this standard. 2. As there have been several industry groups that have stated that an 8 year transition period is not adequate, has there been any response from CENELEC or other national groups ? The transition period is the result of input from National Committees. (CENELEC is not a member of IEC TC 108 or any other IEC committee.) If you do not like the 5-year transition period, comment to your National Committee with both why you object and with your proposal. (I have not heard a National Committee state that an 8- year transition is not adequate. I have heard National Committees state that an 8-year transition is too long.) 3. The oft-heard quote about HBSE is that it is a radical new approach. Other than a new way to draw hazard/protection/product dependency diagrams, what is so 'radical' about 62368 and HBSE ? The new standard introduces models for injury and models for safety. The models allow for prediction of injury. No past standard has used models for its requirements. I suppose one could call this radical. (In the past, most requirements were based on preventing recurrence of a safety incident, i.e., the inversion of a bad experience.) The new standard introduces the concepts of safeguards as the means for protection against injury. If you are not being injured, then one or more safeguards are in place. For many, identification of safeguards is a difficult concept. All of the required safeguards and safeguard parameters are based on engineering analysis. The clauses are organized according to the type of injury. For example, openings for control of electric shock are specified in the electric shock clause. Openings for the control of spread of fire are specified in the fire clause. And, they are different as the safeguard functions are different. If your product poses a fire hazard but not an electric shock hazard, then only the fire openings are required. And vice-versa. Such organization of requirements yields more freedom for the design of equipment. Once you understand the concepts, the new standard is not radical. It is a new and logical way of thinking about safety. Once this new way of thinking is mastered, safety becomes an engineering discipline, much less arbitrary, and not a standards check-off process. 4. To those that have attended the UL seminar on HBSE, and that have previous experience with IT and AV safety, did the seminar enable you to understand and implement any additional or new requirements, documentation, and/or procedures ? No comment. Best regards, Rich - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: A Disk To Reduce EMI from Cell Phones?
Hi Scott: So, I went to the web sites you cited. Then, I went to the citations. For one of the citations, the abstract says: Levels of DNA single-strand break were assayed in brain cells from rats acutely exposed to low-intensity 2450 MHz microwaves using an alkaline microgel electrophoresis method. Immediately after 2 h of exposure to pulsed (2 s width, 500 pulses/s) microwaves, no significant effect was observed, whereas a dose rate-dependent [0.6 and 1.2 W/kg whole body specific absorption rate (SAR)] increase in DNA single-strand breaks was found in brain cells of rats at 4 h postexposure. Furthermore, in rats exposed for 2 h to continuous-wave 2450 MHz microwaves (SAR 1.2 W/kg), increases in brain cell DNA single-strand breaks were observed immediately as well as at 4 h postexposure. C 1995 Wiley-Liss, Inc. The FDA limits cell phone SAR to the head to 1.6 W/kg. Cell phones operate at about 824-829 MHz, and 1850-1910 MHz. I'm not sure how to compare 1.2 W/kg SAR at 2450 MHz with 1.6 W/kg SAR at 1910 MHz or 829 MHz. These frequencies are from: http://www.privateline.com/PCS/Frequencies.htm The Quantum Biology Research paper reports cell phones operating at 2450 MHz. I could not confirm that cell phones operate at 2450 MHz. See: http://www.aulterra.com/en-US/pdf/index/QBResearch2006 This paper indicates the 2450 MHz is from a wireless phone, not a cell phone. Another web site says that the Neutralizer is made from homeopathically enhanced or crystalline matrix mixed into the ink of the Neutralizer patch. These finely ground minerals and trace elements are derived from a rock discovered in Utah... Here are several interesting reports on testing the Neutralizer: http://www.shieldemf.com/files/1690372/uploaded/IIREC_Report.pdf http://www.aulterra.com/en-US/pdf/index/Sun http://www.aulterra.com/en-US/pdf/index/UCIrvine Lots of information out there. Seems like Aulterra has been shipping their Neutralizer around for testing and reports. I wonder if the inventor knows how it works? Best regards, Rich -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Scott Douglas Sent: Saturday, July 05, 2008 12:58 PM To: 'EMC PSTC' Subject: A Disk To Reduce EMI from Cell Phones? Oh Mighty List, Received an email from my sister with information about a product called the Neutralizer which uses a proprietary organic compound composed of natural earth elements which neutralizes the effect of man-made EMF exposure on human DNA. This product comes in the form of a sticker you can apply to your cell phone, computer monitor, etc. such that human DNA can be protected from the damaging effects of RF/EMF. Somewhere I read that it does not block or absorb EMI, but transforms it into coherent and non-harmful radiation emulating organic radiation (my words here). I also read something about a holographic disk. All in all I was rather confused, like I was going in circles. I am not doing a great job of explaining this product so I ask you to visit: http://www.energeticnutrition.com/hi/neutralizer.html and see for yourselves. Scroll down to read all the material, especially the FAQ at the end. I also read one or two of the research papers here: http://www.aulterra.com/en-US/welcome/research. I am not connected in any way with this product, except my sister bought some disks. I am really curious to know if anyone on the list has ever heard of this product? Or would someone else go check out these web sites and let me know what you think? On the one hand, it sounds like the holy grail of EMI fixes. On the other hand, maybe I need to take out a selling license for the product and plan to retire early. All comments welcome, on or off list. Best regards, Scott Douglas sdoug...@ptcnh.net - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
CCC processes
Is there a good document (in English) on CCC processes? How to do it? Are there any agents in England who can assist or get CCC? Thanks for your help, Richard Nute San Diego - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: like your eggs raw /// mobile phone safety
Six Parisian libraries have already been the subject of a campaign of measurements of electromagnetic waves, showing that electric fields were 80 to 400 times below the regulatory limit. The city is aware of concerns and wants to remain vigilant, said Anne Hidalgo, the first deputy mayor of Paris. In November 2007 a moratorium on Wi-Fi in libraries in Paris had been voted by the committee hygiene and safety, and the direction of Cultural Affairs of the City of Paris. The same month, the ministry of ecology and health had ordered a report on radiation, therefore including waves Wi-Fi, report whose publication is scheduled to appear at the end of the year. Will the report include the emissions of the TV transmitters at the top of the Eiffel Tower? I would guess that radio and TV emissions at almost any location would exceed those of Wi-Fi. Richard Nute San Diego - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: 60950-1:2006 clause 2.5 - Limited power sources
Hi Jim: I don't understand why electromechanical devices cannot be proven to have reliable cycle life. There are electromechanical devices tested for 6,000 cycles and 100,000 cycles commonly available, and there may be other classes with even higher cycle life. For a circuit-breaker, why do we need 6,000 or 100,000 cycle reliability? Circuit-breakers probably are not operated even 100 cycles during their lifetime. A circuit-breaker need only be reliable for one cycle -- provided that it fails safely (open circuit). The marketplace will demand reliability, not the safety standards. Best regards, Rich - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Turkish Tabloid -- Spiegel -- Sober -- a brief explanation
Since May 16, worldwide spam messages have been sent containing links to the Spiegel web site. One of those messages found its way to emc-pstc. The spam uses a variant of the mass-mailing worm Sober. This worm taps into inboxes and then sends out infected mail to everyone listed. If emc-pstc is listed in the mailbox, then our emc-pstc listserver will treat the message as a valid posting from a valid subscriber. According to the Spiegel web site, the spam attack was apparently conducted by Germany-based neo-Nazis. You can find a complete explanation at the Spiegel web site under newsletter. Details of the re-appearance of the Sober worm can be readily found on various web sites using a search engine such as Google. I trust you find this explanation acceptable, and will not blame subscribers for this worm-caused breach of our postings rules. If you have any further questions or comments, please contact me off-line. With best regards, Richard Nute Co-Administrator, IEEE PSES emc-pstc Listserver c/o Hewlett-Packard Company San Diego
Virus confirmed,
With thanks to Jim Eichner, the virus is confirmed. Delete the message from RPICKARD. For a complete description of the virus, see: http://vil.nai.com/vil/content/v_127423.htm Note that it spoofs the sender. Also note that the virus was discovered today, August 9. Perhaps that is why the IEEE anti-virus missed the attachment. Also, it seems that not everyone on the listserver mail list received the virus message, which may be due to local anti-virus. Good luck, and best regards, Rich
Re: Security Problem?
Please treat the attachments to Ron Pickard's message as a virus. At the moment, we cannot confirm whether the attachment contains a virus. The file passed through the IEEE virus filters, which are *VERY* good. Also, at least one subscriber checked the files with Norton and did not discover a virus. However, the posting by Ron Pickard, one of our administrators, was NOT deliberate. So, the behavior of the posting as well as the format of the contents suggest a virus. It is possible that the message contains a new virus for which there is no anti-virus. Please do not post further messages about the alleged virus. Such postings dilute the value and service of this listserver. If you have comments about the message or its contents, please direct them to me or another administrator. This is our job, and we are addressing it. As mentioned, please treat the message as containing a virus. Best regards, Richard Nute co-administrator, emc-pstc ri...@ieee.org 858-655-3329 San Diego
emc-pstc Administrative Message
We are changing our listserver software from Majordomo to ListServ. We will announce the date for the change in future message. We anticipate no interruption in service; the changeover should be transparent. ListServ has a number of user-selectable features that are not provided by Majordomo. These features include: * user-selectable digest mode (1 e-mail per day containing all messages) * ASCII or HTML receive mode. * Vacation mode. After the change, we will provide instructions on how to set up your personal ListServ settings. For more info on ListServ, see http://listserv.com. Majordomo accepts messages sent to either: emc-p...@ieee.org emc-p...@majordomo.ieee.org When we change to ListServ, the second address will no longer work. So, please check your address book, and change to the first address. This will assure that you can continue to post messages to emc-pstc. I'm sure you've noticed in recent postings that the IEEE provides effective virus protection. This will continue. Best regards, Rich Nute, emc-pstc co-administrator Jim Bacher, emc-pstc co-administrator
Re: How do I do this test?
Hi Vic: I have a Class 1 product. It has a double insulation barrier between Primary and earthed SELV, and basic between primary and the metal enclosure. How can I perform an electrical strength test across the primary/SELV barrier? The construction you describe has two insulations in parallel: 1) basic insulation between mains and earth, and 2) double insulation between mains and earthed SELV. Since the insulations are in parallel, the basic insulation must be disconnected in order to test the double insulation. One could simply test the double insulation together with the basic insulation and accept the consequences of potential failure of the basic insulation during the test. This is not as horrific as it might sound. Typical solid insulations have electric strengths in the order of 10 kV and more. Air insulation is the weakest insulation in the system, but is renewable so no damage is done to the air (or product) if it should break down. In performing an electric strength test, one can only damage solid insulation. So, the issue is whether or not the solid insulation employed as basic insulation is good enough to withstand the double insulation electric strength test. Almost any solid insulation should readily withstand the double-insulation electric strength test voltage without degradation. In our products, the only solid basic insulations are: 1) the IEC 320 appliance inlet; 2) the printed wiring board; 3) Y-caps. We use Y1 caps, which are equivalent to doube insulation. The only solid insulations that would be subject to over- voltage are the appliance inlet and the PWB. We've not seen any indication that these insulations are degraded by the double-insulation electric strength test. In my experience, the weakest insulation is the air between the pads of the Y-caps on the back side of the PWB. Typical breakdown voltage is 4500-5500 V rms. The minimum clearances required by most safety standards have a great deal of margin between withstand voltage and breakdown voltage. For example, a 2 mm purely inhomogeneous-field clearance (basic insulation) breaks down at 1.68 kV rms. Most constructions have a field that is much better than purely inhomogeneous. For the production-line, we use 4300 V dc, mains-to-earth. Dc tends not to ionize the air as quickly as ac, and therefore is less stressful to solid insulation than ac. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN 61000-3-2:2000
Hi Josh: This standard has been adopted by China and Japan. Japan has added a source impedance for the test setup, but it implies to me that this is a world-wide issue. The question I was attempting to answer was John's question if 61000-3-2 is not an EMC standard, then what kind of a standard is it? The standard was written and promulgated to the IEC by a European committee to solve an anticipated European voltage distortion problem. My contention is that the committee assigned the standard to EMC for the purpose of coming under a Euro Directive that would make the standard mandatory in Europe. I am not familiar with the motivation for other countries adopting the standard as a National standard. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN 61000-3-2:2000
Hi John: Some have questioned whether 61000-3-2 is even an EMC standard! If not, what do you think it is? I fall into the group that question whether 61000-3-2 is an EMC -- Electo-Magnetic Compatibility -- standard. The objective is to prevent reduction of peak voltage on the public supply mains (in Europe) due to rectifier and similar non-linear loads. The method chosen is to require all loads to be near- linear. I suppose this is a compatibility issue -- a compatibility between the source and the load. And, it is electrical. And, one can consider the harmonic content of the current waveform as being an emission from the product. But, this is purely a current emission. It is not measured with a receiver as are the other 61000-series emissions. Unlike radio-frequency emissions, incompatiblity affects no one but the electricity supplier. (Don't argue that other users on the public supply are affected; this is only true if the electricity supplier does nothing at his end.) Non-linear current is not at all similar to the electo- magnetic emissions issue addressed by the other standards in the 61000-series. If harmonic currents are an EMC issue, then so, too, is x-radiation from cathode-ray tubes -- which is a MUCH closer fit. Why isn't x-radiation emission included in the 61000-series? Or laser emissions? Both of these are much better fits to the 61000-series than is a non-linear current. Lastly, this is a Euro-centric issue, not a world-wide issue. It shouldn't be in the IEC scheme. Next thing that will happen is that the 61000-series will include requirements against voltage emission (voltage on accessible parts) to achieve compatiblity with people to prevent electric shock! EMC!!! :-) 61000-3-2 should be a stand-alone standard. But, if it was a stand-alone standard, there would be no Directive behind it to enforce it. So, in a self-indulging mode, and by stretching the definition of EMC, 61000-3-2 is enforced by the EMC Directive. That is why it is an EMC standard. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Peter: The body shape and dimensions, the pin sizes shapes, dimensions and orientations where they interface with an appliance coupler I know are defined. I don't have copies of all of the IEC60320 documents and am unaware that the product interior side of the appliance inlet is defined in those standards. The IEC 60320 does not specify the interior side of the inlet. However, IEC 60320 does specify a minimum spacing of 4 mm between mains and the PE anywhere on the inlet. In the best case, the interior would also meet the same spacings, 5 mm, as the mating face. Some manufacturers include a ridge between all terminals so as to guarantee the spacing is at least 5 mm. Do these standards also control the form-factors so that that one SMD has the same foot print as another? Same for through-hole devices? How the conductors are routed and the other shapes not addressed by a standard could conceivable contribute to DB at a finite potential greater than 2kVac specified in IEC60320-1. No, the form factor and foot print are not specified in IEC 60320. The distance and the conductor shape determine the electric strength of any pair of conductors or conductive parts. The greater the distance, the greater the electric strength. The more homogenous the electric field (created by the shape of the conductors), the greater the electric strength. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Peter and Raymond: To verify the veracity of my memory, I went to my lab and took two manufacturer's C14 appliance inlets and applied 5kVac from both poles to the earthing terminal for 7 mins. each, with the instrument sensitivity adjusted to its maximum (eg, minimum current flow tripping the indicating circuit). Both showed no signs of breakdown, except for a misapplied lead on one of the EUTs (which was corrected as soon as DB was noted as the test potential approached 4.8kV; reapplying the leads more carefully and retesting proved very successful). No typographical error: 5kVac for 7 mins. The C14 inlet has 5 mm between mains and PE. This is a constructional requirement based on the location of the pins relative to each other. As a stand-alone, and having something better than a purely inhomegeneous field, the C14 inlet should readily withstand 5 kV -- forever. However, when wires are attached to the terminals, the clearances are necessarily reduced. Likewise, when the appliance inlet is soldered to a PWB, the traces on the PWB will reduce the spacings to less than 4 mm, and we can expect breakdown in the neighborhood of 5 kV. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Peter and Raymond: In the sake of fairness, it should be noted that both of my EUTs had solder loops and were not intended for surface or through-hole mounting to a PWB. For the sake of our mutual edification, it would be interesting to see how the appliance inlet in Raymond's customer's power supply might perform, desoldered from the board and tested to determine its ultimate breakdown potential outside the power supply. This would be a good exercise for Raymond to also provide his customer with the best possible advice. Raymond doesn't have to do this. The dimensions of the standard C14 specify 5 mm between mains and PE. The dimensions of the pins determine the field shape. These two sets of dimensions set the withstand/breakdown of the C14. Therefore, each and every C14 will withstand 5 kV. The breakdown in Raymond's unit is not the C14 itself, but probably on the back of the main PWB, either where the C14 is soldered to the board or where the Y-caps are soldered to the board. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hello Chengwee: Whether customer can accept his adaptor with only 1500Vac hipot tested where other power supplies can withstand 3000Vac? This is an interesting question as it implies that the higher the withstand voltage the better the unit. The statement may even imply that a double-insulation scheme provides a better safeguard against electric shock than does a PE scheme. In fact, the two schemes provide equal protection against electric shock. There is no *inherent* advantage of one over the other. The 1500-volt withstand value is derived from the normally-occuring mains-to-earth overvoltages plus margin. In other words, the 1500-volt test represents an acceptable insulation that will not fail when subjected to mains-to-earth overvoltage. The 3000-volt withstand value is derived from testing two 1500-volt insulations in series. The 3000-volt test tells us that the two insulations, as a system, are acceptable, assuming that the voltage divides equally across each insulation. (The two insulations will never see overvoltages as high as 1500 volts.) There is no inherent advantage to a unit that passes a 3000-volt withstand test versus a unit that passes a 1500-volt withstand test. The only thing that the 3000-volt withstand test tells us is that the double-insulation system is intact. If I recall correctly, Raymond Li said that the unit in question passes 3000 volts primary-to- secondary, fails 3000 volts primary-to-earth, but passes 1500-volts primary-to-earth. This tells us that both the basic insulation and the double insulation are acceptable. Would that affect his customer Safety testing, because his customer unit with his power supply only meet 1500Vac hipot after heating test? If the customer wants double-insulation throughout the unit, then the adapter is unacceptable. If the customer wants a unit that is certified to a safety standard, then the adapter is acceptable. Or what if Safety agency require his customer unit to do grounding test to accessible metal part? Based on Raymond Li's description and on my own experience, I believe there should be no problem passing the production-line grounding test at 25-amperes. * Despite the preceding comments, such an adapter should easily pass double-insulation requirements between primary and ground, and between primary and secondary. In my experience, adapters designed to IEC 60950 can easily achieve more than 4500 V rms withstand. And, they can easily achieve 25 amperes dc-to-PE. So, I am a bit disturbed that the unit does not pass 3000 V rms to earth. This says to me that there is a clearance within the unit that does not meet the IEC 60950 requirements. I would further guess that the clearance is likely to be an operator-dependent clearance that is determined during the assembly of the unit. (The IEC 60950 clearance dimensions are quite conservative, and should not break down below about 5000 V rms.) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Peter: I have and continue to advocate (in IEC TC 108) that such classes should apply to CIRCUITS, not to products. If this is endemic in IEC (as your statement implies), it may require a elephantine effort. Good luck. Yes. And thank you. The IEC Class I and Class II is an attempt to categorize products according to the supplemental safeguard, i.e., earthing or supplemental insulation, respectively, against electric shock. The IEC Committee that developed the class definitions is an electrical installation committee, not a product committee. I would guess that they had electrical installations, not products, in mind when they developed the definitions. Its fairly easy to encase an outlet box in metal or plastic and thereby get *pure* Class I or Class II products. With the advent of TC 108, supplemental safeguards will be treated as independent supplemental safeguards without reference to the IEC classes. I believe this will demonstrate that the IEC class designations actually confuse product design and evaluation rather than help. (This string is an example of how we get tied up with the issue of IEC Class versus actual construction!) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Chengwee: In my years working in power supply industry, I have never done the ground continuity test between Earth terminal to the DC output for adaptor. Normally I wouldn't trust the PE path with anything less than 18AWG or equivalent. There are two kinds of tests that I have in mind. First is the type test which is done during the evaluation of the unit. Second is the production- line test. For the type test, the test point can be at the site where basic insulation is interposed between the mains and the earthed conductor or part on an unassembled unit. This test does not subject the functional earth to the high current. Many cert houses require production-line ground continuity tests; some require the test current to be 25 amps. So, this test must be performed on the assembled unit and necessarily subjects the functional earth circuit to the same current as the PE circuit. In addition to that, agency such as UL have ramp up the test current to 40A, for 2 min according to the standard 2.6.3.4 for 20A circuit in U.S. As previously mentioned, as a type test, 40 A can be applied only at sites where basic insulation exists between mains and the earthed conductor or part. * The ability of the circuit to withstand high current is a function of the various resistances. The resistances, in turn, are a function of the heating that results from the current. When small conductors are used, the conductors must be short (to reduce the resistance) and heat-sunk. The construction described by Raymond Li likely uses short lengths of 18 AWG between the main board and the EMC shield. The EMC shield provides a good heat- sink for the wire. The main board also proveds heat- sinking. So, for a circuit that comprises a functional earth circuit, it can easily withstand the 25-amp production-line test. Clearly, a PE circuit requires 18 AWG or bigger wire. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Peter: No where does the standard state that by simply providing a Functional Earth, even through an appliance inlet (implying use of a power supply cord), the equipment is not considered Class II. One is simply limited to not marking with the aforementioned symbol. I'd appreciate hearing more from you on this Rich. Unfortunately, the IEC scheme of safety, Class I, Class II, and Class III, applies to products, not to circuits. I have and continue to advocate (in IEC TC 108) that such classes should apply to CIRCUITS, not to products. The IEC 60950-1 standard recognizes that Class I equipment may include some Class II construction. Indeed, the standard expressly states that SELV circuits may be separated from other circuits by double or reinforced insulation and tested accordingly (although the standard does not provide guidance on segregrating Class I and Class II circuits for such testing). With regard to testing the complete product that includes both Class I and Class II construction, i.e., hi-pot and grounding continuity, the applied tests are for Class I, not Class II. This is the point I was trying to express to Raymond Li. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi John: I do have one question for the group just for my own knowledge...back in my TUV days I worked almost exclusively with IEC60950 and seem to remember that a class II product can have a functional earth connection provided Primary and other hazardous voltages are insulated from earth by reinforced insulation. In this scenario even thought the product has an earth connection would it still be considered class II with regards to the IEC60950 standard and have to be marked as such? Maybe it is semantics as you reference protective earth so it must be class I as opposed to functional earth which is not relied upon for safety. Yes, a Class II product may have a functional earth. However, the standard does not define whether that functional earth may be by means of the PE in the power cord. I have always presumed that the functional earth of a Class II product is by means of signal (functional) interconnections to other products that have their functional earth connected to their PE terminal. We don't have functional earthing through a power cord and appliance coupler. These are always built as PE conductors. The appliance coupler has basic insulation between the mains and the PE terminal. So, the use of an appliance coupler REQUIRES that the earthing circuit at the appliance coupler be a PE circuit. (Reference IEC 60950-1, sub-clause 2.6.2, last dashed paragraph.) If the product has an earthing connection via the power cord, then how do we tell the user that the earthing scheme is functional, not PE? We cannot mark the unit with the double-insulation mark. (Reference IEC 60950-1, sub-clause 2.6.2, last dashed paragraph.) My conclusion is that any product with a PE conductor or terminal (i.e., 2-wire + earth) is a Class I product. Any product without a PE conductor or terminal (i.e., 2-wire) is a Class II product. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Raymond: If the dc output is connected to the PE terminal, then the dc output could become live in the event of a fault in the basic insulation between mains and the PE terminal. I think it may not be the case in practice. Even the dc output is connected to the PE, if the basic insulation in the earth terminal should fail, the dc output still safe. It is because the leakage current will go to the earth path (low impedance) rather than the dc output + human body path where has much higher impedance. Agreed. The situation is that the PE must be able to carry the fault current in the event of a failure of basic insulation. Consequently, the PE circuit from the furthest point where a failure of basic insulation may occur must be capable of carrying the fault current -- up to 25 amperes (according to the standard) until the mains circuit overcurrent device operates. If the PE is connected to earth, then the dc output will not rise to the mains voltage. This is the principle of protection in the event of a fault. My reference to live in the event of a fault is the principle behind the determination of what conductors must be connected to the PE terminal and must be capable of carrying 25 amperes for 1 minute. If the adapter is sealed, then the only way to test for earth continuity is to check from the dc output side to the appliance coupler earth terminal. There is a comment from the supplier that the secondary components are not supposed to handle 25A current and unforeseen damage (early failure) may happen. Any comments? The supplier is correct. However, the issue is that of testing the PE circuit after the unit is assembled. This can only be done by testing between the dc output and the PE terminal. This means that the secondary circuit path must be capable of 25-amperes for 1 minute in order to test the PE circuit. In practice, the construction you describe can indeed pass this test. The single-sided PWB earth plane has sufficient cross-sectional area to carry the 25-ampere current. The leads to the PWB from the dc output to the PWB and from the PWB to the PE terminal must be reasonably robust (e.g., 22 AWG) and short length. This prevents these conductors form overheating during the test. I've dealt with a number of these adapters and have had no problems with the 25-amp test, dc output to PE terminal. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Raymond: 1. Earth continuity test As the class 1 is due to the additional earthing plate, how can I ignore the earth continuity test? Class I is due to the adapter having an appliance coupler with a PE terminal. Without this earthing plate, the unit is in fact a class 2 construction. No. If the unit has a PE terminal, then the unit is Class I. The unit may be Class II construction, but if it has a PE terminal then it is a Class I product. Thus, I am a bit confused with such construction and should I follow the required safety tests for class 1 or class 2. For the purposes of testing for compliance to a safety standard, the test for Class I apply. For the purposes of true safety, then the primary- secondary insulation should be tested for Class II. I have another thought that actually, the earthing plate and the DC output plug earthing are functional earthing, not safety earthing, so electrical continuity test using multitester is sufficient and earth continuity test using low voltage and 25A current is not applicable. Yes, the earthing plate and dc output earthing are indeed functional earthing. However, they are connected to the PE, which is insulated from the mains be basic insulation. If the basic insulation should fail, then the PE becomes live. If the dc output is connected to the PE, then the dc output will become live in the event of a fault in basic insulation. In a sealed unit, the only way to test the PE portion is via the functional earthing plate and dc output terminal. So, a 25-ampere current is required to be applied between the dc functional earth terminal and the PE terminal. 2. Hi-pot test The unit passes the hi-pot test at 3,000Vac if the grounding plate and the bridging capacitor are removed. If only the bridging capacitor is removed, the test voltage goes upto about 2,100Vac max. I note that there is breakdown around the grounding plate and the pcd side of mains female connector at the max. voltage. If the unit fails the hi-pot test between the mains and the grounding plate, then the insulation between the mains and the grounding plate is basic insulation. Therefore, the grounding plate (because it is connected to an accessible part, i.e., the dc output terminal) must be connected to the PE and must pass the 25-ampere test. It seems once the production of the converter is completed, proper earth continuity test and hipot test are unable to be done at IQC of receiving warehouse. Any suggestion to do some extend of safety test without destruction of the finished goods is appreciated. The construction you describe will easily pass the tests for Class I construction, i.e., 1500-V hi-pot, and 25- ampere earthing continuity. Unfortunately, you cannot test the double insulation between mains and the dc output. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Chengwee Lai: 2. Earth Continuity or ground bond testing with 25A or higher is not applicable with plastic case and not applicable at the DC output side. It was meant to check the earth protection continuity of a metal chassis. Protective earthing is required for any conductive part that is susceptible of becoming live in the event of a fault. The fault is that of basic insulation. At the mains appliance coupler, the insulation between the mains and the PE terminal is basic insulation. Depending on the individual unit construction, there may be other points within the unit that comprise basic insulation between the mains and the PE terminal. If the dc output is connected to the PE terminal, then the dc output could become live in the event of a fault in the basic insulation between mains and the PE terminal. If the adapter is sealed, then the only way to test for earth continuity is to check from the dc output side to the appliance coupler earth terminal. 3. I believe you will have to use 3000Vac or 4242Vdc between primary and secondary side, unless you have a failure, then there are steps to go through to isolate the failure. The adapter has basic insulation between mains and the PE terminal, and reinforced insulation between mains and the dc output. If 3000 V rms is applied between mains and the dc output (which is grounded), then 3000 V rms is also applied between mains and the PE terminal. This may lead to early failure of the basic insulation. For this reason, Class I equipment is subject to only 1500 V rms hi-pot. (If care is taken in the design such that the basic insulation has an electric strength exceeding 3000 V rms, then the 3000-V test can be applied.) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Class 1 AC/DC adapter
Hi Raymond: Any product with a PE (ground) connection is, by definition, a Class I product. The common adapters you describe, despite being encased in plastic, are Class I products. 1. Function of the grounding plate The primary and the secondary is reinforced insulation and withstands over 3000Vac. Is this plate to change the whole safety protection system from class 2 to class 1? Or the plate is primarily for EMC suppression? The single-sided ground-plane PCB you describe is used to control EMC emissions. It may also be used, as you describe, to electrically ground the dc output. The ground plane has no safety function, per se. While the safety standards require a product to be Class I or Class II, it is physically impossible to build a purely Class I product. Every Class I product necessarily includes Class II construction. You have accurately described the adapter Class II construction (reinforced insulation, primary-to-secondary). In other words, the adapter has both Class I construction and Class II construction. Safety standards ignore this physical true-ism. Any product with a PE is Class I, and is evaluated only to the Class I requirements. 2. Earth continuity test After the unit is completely assembled, should we conduct the test between the earth terminal of the mains plug and the earth of DC output plug? Yes. The earth continuity test is required for any accessible metal part that is susceptible of becoming live in the event of a fault of basic insulation. Within the adapter, the Class I part of the construction has basic insulation between the mains and grounded conductors. Such grounded conductors must be subject to the earth continuity test. Because the dc output is connected to the grounded conductor, the dc output could become live in the event of a fault of basic insulation. So, an earth continuity test must be conducted between the dc ground and the PE terminal of the mains connector (because the unit is sealed, the test cannot be made directly to the conductors where the fault would occur). 3. Hipot test As the unit is classified as class 1, 1,500 Vac is applied between the earth terminal of the mains female connector and the earth of the DC output plug. Actually, the primary and secondary can withstand 3000 Vac. Is it correct test voltage to apply after the unit is completely assembled? Because the unit is Class I, the hi-pot test voltage is 1500 V rms. The hi-pot test is always performed on a fully-assembled unit. You are correct that the primary-secondary reinforced insulation must withstand 3000 V rms. Note also that the primary-foil (wrapped about the outside of the adapter) must also withstand 3000 V rms (because the plastic comprises reinforced insulation to accessible surfaces). While the unit will probably withstand 3000 V rms, you should not production-line test to 3000 V rms because this may overstress the primary-ground insulation. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: FW: Y caps
Hi Brian: Does a cap rate Y2 IAW EN132400 and IEC 60384-14 meet all requirements for the UL CCN for EMI filters (FOKY2, UL1414)? Only if the Y-cap bears the UL mark. Look for the mark on the cap. Is the UL CCN FOKY2 based on UL1283? UL 1414 applies to capacitors which can be used in an EMI filter as well as other safety-related applications. In the UL scheme of the world, the CCN is FOWX2. UL 1283 applies to a complete EMI filter, including chokes, capacitors, enclosure, etc. The UL CCN is FOKY2. To confirm UL CCN and standards data, see the UL web page and use the search tool. (That's what I did to answer your questions.) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Impulse for Hi-Pot
Hi Bryan: I have a request from the design community to implement a routine impulse test in lieu of a Hi-Pot test. This product is evaluated to 61010-1 and the reason for the request is that a measuring circuit connected to the affected output circuit contains a resistor string that cannot withstand the power delivered by the Hi-Pot test [4.6 kVdc across a mom resistor = 4.2 Watts. (this is greater than the 1 Watt resistor rating)]. I am a bit surprised that the hi-pot test would be required in this circuit. Generally, hi-pot is applied to insulations between electrically-isolated circuits. The resistor string you describe bridges the insulation and appears to be sufficiently low that I question whether the two circuits are isolated for the purposes of safety (in particular, protection against electric shock). Or, if the circuits are isolated for safety, then I question whether the hi-pot voltage is too high for this specific application. (If I recall correctly, the hi-pot for measuring circuits depends on the external circuits for which the product is rated to measure.) If you can provide more details about the measuring circuit and the function of the product, perhaps we can give you a better answer. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Hi-Pot testing
Hi Sam: Correct me if I'm wrong, but the point of the type-level hipot test is not to simulate a real-life condition (like surge protection), but to simulate years of insulation degradation, which happens with or without surge protection. I disagree. Primary circuits are subject to overvoltages due to switching of inductive loads such as motors. These overvoltages are NORMAL and, to some extent, predictable. Many studies have been published on the magnitude, duration, and repetition of these overvoltages. Safety insulations in primary circuits must be able to withstand these NORMAL overvoltages. Hence, the hi-pot type test is one measure of the adequacy of the primary circuit safety insulations to withstand these NORMAL overvoltages. The hi-pot type test does not in any way imply reliability of the solid insulation. Failure of solid insulation due to impressed voltage starts with partial discharges in voids in the insulation. Reliability is a function of the magnitude of voltage across any void. The smaller the void, the more reliable the insulation. A perfectly homogeneous solid insulation is very reliable with respect to the impressed voltage. (Many solid insulations approach perfect homogeniety.) An overvoltage limiting device, i.e., surge protector, can limit the magnitude of voltage across a safety insulation. This in turn limits the magnitude of voltage across any void in the insulation. The lower the voltage across any void, the lower the magnitude of partial discharge and the longer the life of the solid insulation. In practice, however, for typical mains over- voltages, the magnitudes, durations, and repetition rates together with the homogeniety of the insulation are such that damage due to partial discharge almost never causes catastrophic solid insulation failure in the lifetime of the product. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Hi-Pot testing
Hi Chris: During safety testing at the lab, the unit passes HiPot testing. However, the unit is broken by the testing. Rigorously, the unit passes its type testing because it doesn't become unsafe by the Hipot. However, it isn't functional after the test; and it requires repair. I have two questions: 1. Is the functional failure due to over-voltage of a component? Or 2. Is the functional failure due to the hi-pot leakage current between primary and secondary? If 1, then you should be able to disconnect that component during the test. Or, you could use the solution for 2. If 2, then the problem becomes much more complex. We test the board before it goes into the product using a bed of nails that equalizes the potential on throughout the primary and throughout the secondary. This prevents current through the components, yet tests the isolation between primary and secondary. Of course, such a test does not test the board in the end-product, which is a problem if the enclosure is metal. Without more details of your circuit and the parts which are broken, I cannot give you further advice. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: fuse replacement markings
Hi Peter: Is anyone aware of any CTL decisions for IEC60950:2000 or -1, where operator accessible fuse replacement marking requirements may be waived, based on the fuse not being required for safety reasons (did not open during any test under any conditions of test) and where of the fuse may be replaced by an operator/user? If the safety tests were successfully conducted with the fuse shorted, then there are no marking requirements. The fuse becomes a functional part, not a safety part. However, safety standards assume a fuse is only used for safety. So, the safety standard marking requirements automatically apply to all fuses. CB certification houses are reluctant to deviate from the standard for fear of being criticized by other certification houses who will use the CB. So, to avoid possible criticism, they will take the conservative position and impose the marking requirement and will be highly reluctant to deviate from the standard. You MAY be able to get the cert house to explain in the report that tests were conducted with the fuse shorted, and therefore a fuse replacment marking was not required. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: 94V-0 question
Hi Dave: I need a sheet of plastic that goes between a PCB and a metal enclosure. This is to make a creepage spec. What plastics are good for this? Will polycarbonate be suitable and have a 94V-0 rating? With respect to IEC 60950... A plastic material used as an electrical insulator (creepage) has no flame-rating requirement. Rather, the material must be a suitable insulating material. Most plastics are suitable insulating materials. Check the UL electrical ratings for your candidate materials. If you are seeking UL certification or equivalent, then the material must be a UL-recognized plastic. If the material is within a fire enclosure, then the material must be V-2 or better. If it is not within a fire enclosure, then there is no flame rating requirement. If you are placing the material between the PCB and the metal enclosure, then I suspect you really mean clearance, not creepage. A creepage is a distance along the surface of an insulator. If the PCB abuts the metal enclosure, then it would indeed be a creepage (as well as a clearance). If the PCB does not abut the metal enclosure, then it is a clearance. This is a very important distinction. If the clearance does not meet the necessary distance, and if the metal enclosure is grounded, then the sheet insulator comprises Basic Insulation (and there is no thickness requirement). If the metal enclosure is not grounded, then the sheet insulator comprises Reinforced Insulation, in which case the material thickness must be 0.4 mm or more. Good luck, and best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: NARTE safety engineer certification
Hi Peter: Out of curiosity, I wrote NARTE directly regarding the below, to see what benefit they believe NARTE certification would offer someone who already has experience in product safety and a PE Registration. It's been a week and they have not responded. Perhaps that's their answer. I asked for their registration forms. I have yet the hear from them. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: The transformer screen/shield conundrum
Hi John: If the breakers are 230 V/16 A and 120 V/15 A, then the power distributed at 230 V is roughly twice that at 120 V. But your '120 V' is also '240 V' for some equipment. Besides, I think I was being 'generous'; electrical energy consumption per head in USA is probably greater than in Europe. In North America, the 240 V is supplied to high-power- consumption equipment such as water heaters, electric ovens, electric cook-tops, electric clothes dryers, electric furnaces, and air conditioners. The 240-V circuits are rated 20, 30, and 50 amps. In North America, typical equipment is not rated for use on 240 V, but 120 V. While 240 V is supplied to each home, use of 240 V for applications other than those I mentioned, would require a special electrical installation. This is extremely rare. So, you can't really consider North American 240 V mains circuits in this discussion. We don't. * I do agree that electricity consumption per head in North America is probably greater than in Europe. Having lived in Spain, I believe that North American appliances are bigger and therefore consume more electricity. Also, NA electrical appliances tend to be less efficient than Euro appliances. NA clothes and dish washers use much more water than Euro versions. * Neither of these topics has anything to do with the current available into a fault before the circuit breaker operates. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: The transformer screen/shield conundrum
Hi John: For 3% voltage drop at maximum rated load, the source resistance is about 0.2 ohm. So the maximum rms current would be system nominal voltage divided by 0.2 ohm, or 600 amps for 120 V and 1150 amps for 230 V. For 230V, there are two modifications. One is that roughly the same *power* is distributed as at 120 V, so the system impedance would be doubled. But, in addition, the supply voltage tolerances are greater than 3%: in Europe the tolerance is about double, so, overall, the system impedance could be four times that 0.2 ohm. But in fact, 90% of supplies are below 0.47 ohms (see IEC 60725, under amendment). I disagree that the same power is distributed at 230 V and 120 V. If the breakers are 230 V/16 A and 120 V/15 A, then the power distributed at 230 V is roughly twice that at 120 V. My subject was *not* supply voltage tolerance, but system *design* goal for percent voltage drop at max rated load (the circuit-breaker rating). I really believe that EEs in Europe design supply systems to 3% voltage drop at rated current, 16 A, just as they do in North America. The reason I so believe is that the wire sizes for 15 A (NA) or 16 A (Euro) circuits are nearly the same. The same size wire at (nearly) the same current would give (nearly) the same percent voltage drop. (If the system source impedance is 0.47 ohms, then, at 230 V, the system voltage drop would be slightly more than 6% at maximum rated load.) We really weren't talking about voltage, but about the maximum current into a fault in cord-connected equipment. The voltage tolerance can be ignored for this purpose. That still gives 490 A, which would be embarrassingly big, but it apples at the 'point of common connection', not at the wall socket and still less at the equipment. My comments were for the current available at the wall socket. In North America, building wiring is designed for maximum 3% voltage drop at maximum rated current. In NA, at the point of common connection between the building and the electicity supplier, the electricity supplier maintains a nearly constant voltage. He does so not only by his system design, but also by dynamically adjusting the voltage of the source. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: The transformer screen/shield conundrum
Hi Richard: You mention a few times the 25 Amp test. The designs I have seen that try and use this approach (and I don't ever recall seeing a design I was happy with) were all switch mode power supplies where there was an input fuse of about 2A, meaning that the test would be performed at 3A in the past (and will be performed at 4A in the future, if the CDs go through un-changed). I'm surprised that, today, a SMPS would used screen/ shield construction. The effectiveness of a SMPS transformer is a function of the physical proximity of primary and secondary windings. All of the SMPS transformers that I have been involved with over the past 10 years or so use reinforced/double-insulation between primary and secondary. While I mentioned the 25-amp test, I fully concur that the test current is a function of the relevant overcurrent device. problem I am not convinced that it is the whole story. For me, another chapter in this story is the part played by the very high surge current that flows for a very short period of time. It is here where we could usefully I presume you are referring to the circuit prospective current. (I am not familiar with the proposal to WG8.) I would agree that this current, at a very small contact area, is the driver for the hole in the screen/shield. However, I believe that the circuit prospective current is of little or no consequence when testing a robust earthing circuit complying with the constructional requirements. (Of course we should test this hypothesis.) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: CE without LVD?
Hi David: In regards to your suggestions below, would it not be wise to take into consideration the future plans of the LVD? The original question was specific to the LVD. My response was specific to the LVD. You raise a new question with regard to a future EU directive, the requirements of which may very well be quite onerous, and possibly quite out of line with the three-block models for injury and safety, from what I've heard. Each manufacturer should keep abreast of the EU activity, and decide for himself as to what action he should take now in anticipation of a future directive. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
The transformer screen/shield conundrum
Hi John and Richard: The transformer screen/shield between primary and secondary windings is intended to carry the fault current in the event of a failure of basic insulation between the primary and the screen/shield. The screen/shield must be capable of carrying the full fault current and is often tested using the 25-amp test. The object of the test is to connect to the screen/shield, and then pass the 25 amps through the shield to its transformer terminal and then to the PE terminal. The difficult part is how to connect the tester to the screen/shield. When the screen/ shield is a copper foil, a special transformer must be wound with a wire connected (soldered) to the foil screen/shield and brought out for connection to the 25-amp source. If this cannot be done, then a wire is soldered to the edge of the foil screen/shield by forcefully separating the sheet insulation that extends beyond the edge of the shield, inserting the soldering iron tip, and soldering the wire. (A constructional problem is that the screen/ shield must extend BEYOND the primary winding so that no part of the primary winding is exposed to the secondary winding.) (Another constructional problem is that the ends of the foil must be overlapped, but with insulation inserted between the overlaps; otherwise, the screen/shield would constitute a shorted turn and cause all kinds of electrical, magnetic, and thermal problems.) The connection of the tester to the foil screen/shield typically has a very large contact area. Any thickness of foil screen/ shield passes the test. The conundrum is that the failure of basic insulation could result in a point contact between the primary winding and the shield. The point-contact, because of its small area, has very high current density, and will blow a hole in thin foil (that otherwise passes the 25-amp test). With the hole in the screen/sheild, the fault to the foil opens, and the fault no longer exists -- even though there is a failure of basic insulation. The connection of the foil to the PE remains intact, and there is no shock hazard. (Of course, the heat of the point-contact fault may very well cause failure of the foil screen/shield-to-secondary functional insulation, which might very well result in a shock hazard from the secondary SELV circuit.) The point is that the test does not necessarily test what can occur within the transformer, yet will pass the transformer screen/shield construction. Nevertheless, when the basic insulation fault occurs, the hole in the screen/shield may very well end the event safely. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: CE without LVD?
Hi David: It is being suggested that this product does not need safety testing and does not need to include the reference to EN 60950 and the LVD in the CE DoC, since it is SELV circuits only. The LVD applies to products with voltage ratings between 50 and 1000 V ac and between 75 and 1500 V dc. SELV does not exceed 30 V ac and 60 V dc. Therefore, the LVD does not apply to a product that operates from a SELV source of supply. (We may be able to say that the LVD does not apply to a Class III product.) However, it is appropriate to indicate in the DoC that the LVD does not apply to the product because the product voltage is below the lower limits of the LVD. HOWEVER... EN 60950 applies to products powered from a SELV source of supply. The electric shock requirements do not apply to such products, but the other EN 60950 requirements do apply to such products. These other requirements include the so-called energy hazard requirements, mechanical requirements, and fire requirements. So, the product does indeed require safety testing, but not with respect to the LVD. The DoC should indicate compliance with EN 60950. Pragmatically, since you must test for compliance to EN 60950 for these other requirements, it is just as easy to indicate compliance to the LVD via EN 60950 and thereby avoid any future argument whether the LVD applies or not. Most of our inkjet printer products are powered by an external SELV source of supply. We test to EN 60950 and declare compliance with the LVD. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: PCB marked for UL 94V-0
Hi Doug: The question is, how do I independently validate the material used, since a vendor could theoretically choose whatever they want and stamp it as V-0? I interpret your question as to how to determine whether or not a PCB is counterfeit or not. A UL-certified PCB would have the following markings: PCB manufacturer's indentification; manufacturer's grade designation; UR mark; flammability rating, e.g., V-0. So, it is not just a matter of the V-0 mark; all four marks must be included on the board. I suppose a vendor could counterfeit all four marks. If I had a suspect PCB, I would first confirm the PCB manufacturer and grade designation as being in the UL Yellow Book. If they are not in the Yellow Book, then that confirms that the PCB is counterfeit. If the marks are confirmed by the Yellow Book, then the problem of determining a counterfeit is much more difficult. Unfortunately, testing the board to V-0 requirements will not tell you if the board is V-0. The problem is that the copper traces provide effective heat-sinking for the board material such that even an HB material may pass the V-0 test! (I've actually tested an HB board where the HB material did not extinguish in 10 seconds or 30 seconds, but extinguished in less than 60 seconds!) The only way to confirm V-0 is to test a board with no copper. This means you must peel off the copper from a 1/2-inch by 5-inch section, and then test the section per UL 94. (You must also remove the solder resist.) You can't remove the copper and solder resist by chemical means as this may change the properties of the board material, and you would not be able to confirm the flammability rating. In my experience, I've never had occasion to suspect a PCB as being counterfeit. We've never bought a board from a non-UL vendor. While I suppose there are non-UL vendors, I suspect there are very few. Good luck! Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Bad Fuse vs. Good Fuse
Hi Dan: Thank you for giving us straight answers and helping us to overcome the conventional wisdom about fuses. Several years ago, I put together an article addressing fuses, their operation, and how to select the fuse rating. See: http://www.ewh.ieee.org/soc/emcs/pstc/psn/ Then, download file 90v03n3.pdf. Clearly, this is out of date, but the principles I believe are still valid. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi Richard: is the below information true for both the AC and DC hipot methods? Some companies have contractors,subcontractors, incoming and final hipot... so it does and can occur at least 4 times, before its shipped to a customer. The theory says that the onset of the breakdown process starts with partial discharge in voids within solid insulation. Partial discharges occur more rapidly with change of voltage. Therefore dc voltages have a lower deteriorating effect than ac voltages. I have a colleague who, for this reason, insists on dc voltage for production-line tests. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi John: There is a justification for a high-current test **where it won't cause any new damage**. The justification is that it will find bad joints in the PEC path, and stranded PEC and bond wires that have only one or two strands still intact. The high-current test will NOT find bad joints. The high-current test WILL find bond wires that have only 1 or 2 strands, and marginally for 3 strands. Finding strand damage is a function of the heat sinking provided to the remaining strands. See: http://www.ewh.ieee.org/soc/emcs/pstc/psn/ Download: 97v10n1.pdf 97v10n2.pdf These describe the experiments I performed on both strands and joints. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi John: I don't think you can draw universal conclusions from just one experiment. In addition, the rate of increase of voltage is limited in the test procedures. In your experiment, there was only one increase of voltage, whereas in repeated testing, there are many. At best, we don't know if that matters or not. My test involved several different units from different manufacturers connected in parallel. The applied voltage was 60 Hz, so there was continuous change of voltage, which is the worst-case for inducing dielectric breakdown (compared to dc or an impulse). If you do a web search, you will find that the numbers I mentioned are in line with those published in web articles and research. For example, see: http://www.quin-t.com/pdfs/cequinvaramid.pdf http://www.wmea.net/partial_discharge_theory.htm http://literature.agilent.com/litweb/pdf/5965-5977E.pdf This last web site has curves showing wear-out curves for optocoupler insulation, both steady-state and impulse. These curves correspond to my findings from my tests (which were power supplies for IT equipment). I stand by my statements. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi John: My last (3) employers have required all repaired or modified units to be hi-potted. If a unit has been repaired, then the cover was removed, and the unit is no longer controlled by the oroginal production hi-pot. I think this is too stringent. Repeated hi-pot tests must be *minimised*, because of the possibility of progressive degradation of insulation. Yes, indeed, repeated hi-pot tests must be minimized. However, significant degradation of modern insulations at these low voltages and durations is doubtful for the lifetime of the equipment. Some years ago, I undertook a test to determine when an insulation would fail if subjected to a continuous hi-pot voltage. I connected several units to the hi-pot voltage for 8 hours/day. The units started failing after about 10 days. That would be about 48,000 minutes. So, we can say that we should probably not exceed 1/1000th of 48,000 minutes, 48 minutes, of hi-pot test time for the equipment lifetime. That would be 48 1-minute hi-pot tests. I don't believe any equipment would be so tested. Now, the transients are only 50 microseconds. 1.2 million transients would comprise one minute of degradation. As I recall, an industrial site would incur 5-10 such transients per day. That means, about 120,000 days for an accumulation of 1 minute of overvoltage. That's over 300 years. While repeated hi-pot tests must be minimized, the degradation due to repeated hi-pot tests is not likely to have an effect for the lifetime of the equipment. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi Gregg and Barry: Australia has an actual standard which lists the tests and procedures for the regular testing of equipment in use, and equipment that has been So has the UK. it was called (something like) The Electricity at Work Act generally a good thing put a dangerously and poorly implemented concept that allowed untrained unprofessionals to destroy a huge amount of IT equipment and charge the customer for it. As a result we had several thousand monitors damaged by 25 Amps being passed between the RGB Coax- grounds and PEG Another anecdote (read horror story) from the UK requirement for periodic safety testing... We had the unfortunate experience of the same UK requirement for periodic testing of Class III equipment for 25 amps from accessible conductive parts. This test destroyed a run on the circuit board, which was a failure of the 25-amp test, which resulted in destruction of the unit! The customer demanded replacement of the units because they failed the test! He did not realize that the test itself was causing the failure, nor that the test was causing destroying the unit. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Glow Wire test vs. UL94 - flammability rating
Hi Ilan: I was looking for a viable comparison between glow wire and the UL94 flammability rating. The point of this little comparison is to bypass the glow wire test for materials, which are properly rated for UL94. There is no comparison between the glow-wire test and the flame test. The glow-wire test is an attempt to ignite the material from a non-flame source. I would guess that ignition of a material largely depends on the type of flame- retardant additive, i.e., whether or not it operates in the gas phase or some other mechanism. The UL 94 test is a measurement of the burning time and the glowing time after flame ignition of the material. In this test, all materials ignite; they differ in the duration of burning after ignition. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: reinforced insulation - EN60950
Hi Alexandru: 1. Is the combination of Basic Insulation + FuseTransorb(15V) equivalent to Reinforced Insulation? No. The scheme of protection against electric shock relies on passive devices, not active devices. As a general rule, active devices, e.g., transorb, are not allowed as equivalent to one element of a two-safeguard scheme, i.e., basic insulation and supplementary insulation. For example, a GFCI/RCCB/ELCB could not be used as a substitute for supplementary insulation because it is an active device. Active schemes are permitted where additional enviromental conditions may exist that could bypass either or both Basic Insulation and Supplementary Insulation (or Reinforced Insulation). For example, GFCI/RCCB/ELCB is required for environments might be wet, where that wetness could bypass the insulation. Another general rule is that deliberate operation of a fuse is not permitted. (I do not have the rationale for this rule.) (Your characterization of Basic Insulation + Fuse Transorb as equivalent to Reinforced Insulation is incorrect. Reinforced Insulation is defined as a single, robust insulation equivalent to Double Insulation. The fact that your scheme includes Basic Insulation as an element means that the system cannot be Reinforced Insulation. A better characterization would be equivalent to Double Insulation.) 2. Does the transorb have to comply with a specific EN safety standard (like one applicable to Y caps)? Yes, if one exists. In the situation you describe, the transorb must be able to dissipate the full mains voltage and current, where the current is the circuit prospective current, for the maximum duration of the fuse, and still be operative for the next such event. Additionally, the transorb would need to dissipate the mains current at a current just below the fuse operating point, and do so indefinitely. And, there would be additional requirements. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Listserver delays -- Re: reinforced insulation - EN60950
Strange behavior of the list-server. Although I got some out-of-office replies, neither I or my fellows in the office (members of the list) have received the message posted 24 h ago. I'll try again... We are still experiencing delivery problems from the listserver. The IEEE gurus are at work trying to solve the problem. We thought it had been solved last week, but we're still experiencing difficulties. Basically, the difficulties show up as very late delivery (and occasional duplicate delivery) to the subscribers near the end of the list (which includes me). Very late can mean DAYS late. Normal time for delivery to the full subscriber list is 3-4 hours. Messages are sent in sequence to the subscriber address list, where long-time subscribers near the head of the list get their messages first, and so forth through the address list. At the moment, it appears that subscribers near the head of the list have normal service. However, subscribers near the end of the list (~700 and above, which would be those who subscribed in the past year or so) are experiencing significant delays, more than 24 hours. If the subscribers near the head of the list set their mailer with an Out Of Office message, then that message is sent immediately to the person posting the message. For posters near the end of the list, the OOO message will be received BEFORE the listserver message. (Indeed, this is the case even when the listserver is operating normally.) Please bear with us while we solve the problem. If you have further questions or comments, please send them directly to me or any of the administrators at the bottom of this message. Best regards, Rich Richard Nute IEEE emc-pstc Listserver Administrator ri...@ieee.org This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: DERIVATION OF CREEPAGE AND CLEARANCES
Hi Gordon: Does anyone know from where the values for creepage and clearances given in EN61010-1 (safety requirements for electrical equipment for measurement, control and laboratory use - part 1 general requirements) are derived i.e. are there other standards below 61010 in this respect? From my review of an early version of IEC 61010, the creepage and clearance values in that early version were derived from IEC 664. Why are you asking? Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Symbols vs. text - was EN61010-1, Symbol 14 - validation
Hi Pete: This usually means developing a focus group and getting them to pick it out of a group of symbols when asked to identify the symbol for 'XXX'. I take this to mean that the group is given the definition and then asked to identify the symbol that matches the definition. Isn't this backwards? Shouldn't a symbol be validated by showing the group the symbol and then asking for the meaning? Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Symbols vs. text - was EN61010-1, Symbol 14
Hi Richard: Products should be designed so that no safety symbols/words are required (at least for the user/operator). A very laudable viewpoint and one that is easily achievable in the examples you provided. However, with certain products there has to be a residual risk or the product simply will not function. Show me an electric chainsaw that has no residual risk and I'll show you a piece of worthless junk. I don't recall my gas chainsaw as having any safety symbols on it. The example of a chainsaw necessarily invokes, under the HBSE scheme of the safety world, behavioral safety. Behavioral safety is when the safety of both you and others is dependent on your behavior. The prime example is that of driving a car on a public road. Behavioral safety necessarily assumes training in the equipment operation, including safety operation. Our discussions are directed towards equipment safety, especially in regard of insidious hazardous energy sources. This topic is very much different than safety of obvious hazardous energy sources. Symbols are mostly used to provide information about insidious hazards rather than obvious hazards. Best regards, Rich ps: I assume your reference to residual risk is the same as defined in ISO/IEC 51. If you are interested, I have a comparison of this document to HBSE which I would be happy to send to you. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Symbols vs. text - was EN61010-1, Symbol 14
Hi Richard: You said We in the product safety industry must be very careful that we use symbols in strict accordance with their definitions. No issue with you there. However, the paper states that some of these misuses were perpetrated by people not even connected with electrical engineering, let alone safety. Indeed. We need to keep such people from learning about our safety symbols (except when we use them in the proper venue and context). :-) This brings me to another of your statements The fact of misuse of symbols dilutes the meaning of the symbol. The more the misuse, the less valuable the symbol is for safety purposes. Perhaps this is true, let's assume it is for the moment. What then are the options available to us? Either we have to find a way of policing the use safety symbols or we have to face the possibility that every symbol described in IEC 60417 could become unusable due to misuse. Any suggestions on how to police (internationally, of course) the incorrect use of IEC and ISO symbols? We need to first make sure our house is in order. First, do we have clear, unambiguous definitions for our safety symbols? Based on the very short definitions in 417, I think not. I believe we need much more work on the definitions. Second, we need to make sure we only use the symbols in accordance with the definition. We can police ourselves through our traditional third-party safety certification of products. So what do we do as regards written words? We look at the context in which the word is used. If I were to pronounce that an object is cool then the chances are that I would mean that it is below room temperature - but if my daughter were to pronounce an object cool then the chances are that it would be the latest 'in thing'. Confusing? In theory maybe, in practice not really. Of course, the standards for word definitions (which, for the sake of simplicity, I'll call dictionaries) do describe multiple common uses of individual words (including examples of their contextual usage, if they're any good). The preceding is a very good statement of the problem of multiple definitions for both words and symbols. Let's back up a step and ask the purpose of the symbol (or even the set of words). I submit that the purpose is to invoke an action on the part of the reader. If the symbol/words is in regard of safety, then I submit that the action invoked is because of lack of a suitable safeguard. Products should be designed so that no safety symbols/words are required (at least for the user/operator). If you look at your monitor, keyboard, and computer, you probably will see no symbols or words relating to safety. So, products CAN be designed without the need for safety symbols. You ask So what do we do as regards written words? My response is design the product so that no words or symbols are needed insofar as safety is concerned. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN61010-1, Symbol 14
Hi Richard: As you say, this web site provides a discussion on the exclamation symbol. However, the discussion is slanted in one direction that not everyone in the safety fraternity would necessarily subscribe to. For instance, I have seen the 'high voltage flash' sign used as a symbol in an internet cafe' - among other misuses. I'm sure that others have examples of symbols defined in IEC 60417 being misused: does this mean that they are no longer usable for safety purposes? The fact of misuse of symbols dilutes the meaning of the symbol. The more the misuse, the less valuable the symbol is for safety purposes. Multiple uses (or misuses) implies multiple meanings. Multiple meanings create confusion in the mind of the beholder. To quote the paper: The power of the safety alert symbol to highlight a safety concern is diluted when the symbol is used for a myriad of lesser tasks. Each non-safety appearance of the symbol produces an anti-teaching effect. We in the product safety industry must be very careful that we use symbols in strict accordance with their definitions. Perhaps you were not intending to endorse the viewpoint expressed? Please confirm. My comment was: For a history and discussion of this symbol, see: This was nothing more than a reference. I feel the reference provides some interesting and useful information in regard of the symbol. I would hope that my statement did not imply endorsement of the proposal presented in the document. I feel the article provides some reasonable ideas for general understanding of symbols along with specific criticisms of the safety alert symbol. I agree with some of the conclusions, but not all. Conclusion 1: Agree. Conclusion 2: Neutral, because the symbol is arbitrary. Conclusion 3: Not applicable; applies to lockout tags. Conclusion 4: Agree with first sentence; disagree with second sentence. Conclusion 5: Emphatically agree. Conslusion 6: Agree. Conclusion 7: Neutral, because this is a proposal. Conclusion 8: Not applicable to endorsement. I do not endorse the proposed international safety alert symbol presented in the paper. I would guess that few or none have endorsed the proposal as it is 2-1/2 years since publication of the paper and I have seen no movement for adoption. The characters (letters) that comprise this message are symbols. We arrange these symbols into words. Each word has a definition; some words have more than one definition. The more definitions a word has, the more chance for confusion as to which definition is applicable in a specific use. Indeed, the definition of words is taken only in the context of a sentence (a group of words) or even a paragraph (a group of sentences). Without a definition and a usage, a word is simply a group of letters. (Stare at one of these words for a few moments and you'll see what I mean.) (Actually, letters and words represent sounds that we utter. Misspelling of words without loss of the sound does not lose the meaning of the words. There is a famous poem about a pea sea spell-checker that demonstrates this concept. A symbol does not represent a sound that we utter; therefore, a symbol is highly subject to misunderstanding.) So, too, for safety and other non-word symbols. Each symbol has a definition. As with words, many of us simply don't look up the definition before we use the symbol (or word). Consequently, symbols are often misused. The more the misuse, the less useful the symbol (or word). Symbols usually don't represent a single word, but rather a phrase or even a complete sentence. Abstract and arbitrary symbols simply don't/can't have obvious definitions. For this reason, we in the safety industry must be very careful to only use safety symbols in strict accordance with their definition. A personal note: Having lived in Spain for almost two years, my wife and I had appliances with nothing but symbols on them. Not having grown up with these symbols as would a local person, we found ourselves quite confused by many of the symbols on our washing machine, dryer, dishwasher, TV, and stereo. Symbols are NOT a panacea for non-language conveyance of information. Nor do the comprise an international language. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line.
Re: EN61010-1, Symbol 14
For a history and discussion of this symbol, see: http://www.triodyne.com/SAFETY~1/sb_v17n2.pdf Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Non-Compliant Products
Hi Enci: Only this morning have I just tested a competitive product from a manufacturer in Germany, which failed miserably (+40dB) on conducted emissions testing and earth leakage, to be fair only 2mA, but the standard clearly states 1mA!. What standard specifies 1 mA? The irony is that leakage current is largely due to Y capacitors in the EMC filter. Higher leakage current suggests higher value Y capacitors. Higher value Y capacitors implies lower conducted emissions. Best regards, Rich ps: IEC 60950 is the applicable standard for IT equipment. The leakage current limit values in IEC 60950 are: 0.25 mA for parts and circuits that are not connected to protective earth, and 3.5 mA (0.75 mA for handheld equipment) for parts and circuits that are connected to protective earth. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Non-Compliant Products
Hi Enci: How about as a consumer, buying a PC, then 6 months later (with no modifications) finds it is non-compliant (highly likeyl!!).. Can the consumer return it/demand correction/!?!? The consumer can always attempt to return a product or demand correction of a non-compliant product. The real question is whether the store or the manufacturer will agree to refund or correct the product. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Administrative message: allegations of non-compliance
The recent string with the subject OK, what's going on? alleges that a named manufacturer's product does not comply with a requirement. We feel that, in the case of a negative or derogatory comment or allegation (in this case non-compliance), the manufacturer (or individual) should NOT be named. We take this from the good manners adage, If you can't say anything nice, don't say anything at all. Similarly, we feel that our subscribers should not publicly announce (read threaten) in this forum that they intend to turn in non-compliance to regulatory authorities. Rather, we suggest that any alleged non-compliance matters should first be brought to the attention of the manufacturer -- privately. We're all friends in this group. We help each other with various technical problems. Non-compliance is a technical problem for which there are several solutions, fix the product, fix the standard, or fix the measurement. In arriving at a solution, please don't denigrate a colleague or a manufacturer (or anyone else, for that matter!). If you want to discuss this matter further, please do so off-line. Best regards, Richard Nute Co-administrator, IEEE emc-pstc listserver. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: product safety audit scenario
Hi Gary: Your comment triggers another comment: Leadership. Typically, we tend to let the inspector be the leader for the duration of the inspection. The host can be the leader. The host can set the agenda (in advance, although the inspector need not be notified). First, is to decide what products to be inspected. Then, decide whether everything will be inspected, or just some individual items, i.e., what does the inspector want to see (decided before going to the factory floor). On the factory floor, the host can then find each item and show it to the inspector. Point-by-point through the whole FUS document. It works well. Some inspectors may tend to feel as though they are being railroaded, so you need to be sensitive to this. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Measuring Power Supply Output Current
Hi Rick: On the surface it seemed like a simple exercise of putting a DC current meter in series with each of the outputs. Given that the current demand for each of these outputs is dynamic, corresponding with the processing activity, does it make sense to measure this output current with a True RMS meter? Since you said you wanted to baseline output power, then you would want to use a true-rms meter. Power is a measure of the electric energy that could be converted to thermal energy. Consequently, you must measure any ac component with a true-rms meter. A true-rms meter will measure both dc and ac. However, this may not give you what you want if the dynamic periods of current change are longer than the period of the meter measurement. However, if you get a constant current reading, then you are getting an accurate measure. If this is the case, I would assume that the True RMS meter takes the measurement based on some type of a time weighted average or sample time. Do any of you have a feel for how this is calculated? There are basically two kinds of true-rms meters. The first kind essentially converts the energy to thermal energy, and measures the temperature. The second kind does an analog-to-digital conversion, and then calculates, point-by-point, the rms value of the waveform. If you have access to an electronic instrument museum, you can use any analog meter that has an iron-vane meter movement. RMS = Root of the Mean of the Squares of each increment of the waveform. How do manufacturers of these PC supplies address the maximum output current ratings for each voltage. Does this rating take into account PEAK demands for current (or over current)? Most power supplies are rated according to the maximum continuous load. The ratings for multiple-output supplies is when all outputs are loaded to their maximum continuous load. (Typically, if any one output is loaded and all others are not loaded, then that one output can be quite a bit higher than its rating. But, this is taken as a fault condition in the load.) Peak ratings are specific to the power supply and its application. Essentially, the peak rating (and its repetition) are determined by the output storage capacitor, both discharge time and charge time. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: product safety audit scenario
Hi Alice: Scenario : Component A with rating mentioned in the UL's product report as 90-135/180-265 Vac, however in the phyical unit is written as 115/230 V . Q1 : Is this a non conformity ? Should a VN be raised ? Yes, this is a non-conformity. In this case, the report should be revised to match the marking on the component. Whether or not a VN is issued depends on the zeal of the individual inspector. If a VN is issued, then you have a formal duty to request a revision to the report. If a VN is issued, it should not include a production hold. If it does, then you should refuse to sign the VN. Instead, telephone or FAX your UL engineer and request a waiver until the report is revised. Scenario : In the report, it mentioned component B carries many safety agency certification, however i the actual physical unit, it only containes one or two safety agency logos. Q3. Is this a non conformity ? Should a VN be raised ? Maybe this is a non-conformity, and maybe it is not. Clearly, one mark is not many, as many implies more than one. If the report uses the word many, then the report is wrong. This is because the report should either specify the cert marks required for this application, or it should not mention the cert marks. In any case, the report should not force the inspector to decide how many marks comprises many marks. If a VN is issued, then you have a formal duty to request a revision to the report. If a VN is issued, it should not include a production hold. If it does, then you should refuse to sign the VN. Instead, telephone or FAX your UL engineer and request a waiver until the report is revised. Q4. When an IPI ( Initial product inspection ) is carried out, should the UL's product report been approved by the UL ? Absolutely. A UL inspection, whether an IPI or a quarterly inspection, is basically a process of comparing the product to the description in the UL report describing the product. Otherwise, there is no inspection as there is no report to compare the product with. An IPI cannot be made to a non-UL product report. If a discrepancy is found, the inspector is not technically qualified to decide whether or the report is wrong or the product is wrong. The VN formally initiates the process to correct one or the other. Q5. Should the report used during IPI is a detailed report with Sec general and condition of testing been included ? At each inspection, whether IPI or quarterly, the inspector is entitled to inspect to both Sec General and to the Sec with the specific product. For an IPI, I would especially expect an inspection to Sec General. This is because this is UL's first visit to your facility, and they will want to examine all aspects. Q6. Can anyone share with me the correct ways the product report/FUS procedure for a product should be written so that we are not caught up with it, particularly on the rating,model and safety agency certification requirement for the product ? When the UL report arrives, you should conduct your own inspection. Go to the production-line, and compare the product to the report. Identify all discrepancies, and make the appropriate corrections to either the product or the report. Then, using a marked-up copy of the report, send the report to UL along with your request to make the indicated changes. If you keep a calendar of UL inspections, you can generally predict the next inspection within a week. A week or so before each UL inspection, you should perform your own inspections, and make appropriate corrections to either the report or the product. On your UL inspection calendar, keep a chart of VN issues per inspection date. Set a goal of 0 VNs. If you do pre-inspections, you can drive the VNs to 0. By doing your own pre-inspections, you will get a feel for problems in the written report. Then you can write reports that will not result in VNs. Speaking from experience, this process works! An inspection is a simple process of comparing the product to the report. Anyone can do this. A VN can be issued for any discrepancy. Do not sign a VN that does not identify a report statement for which the VN is being issued. (Sometimes, this will reveal secret, unpublished requirements!) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are
Re: North American Production-Line Tests; ANSI or Other
Hi Peter: I am trying to find the rationale why production-line ratyhing tests in North America are usually done with a simple ohmmeter and without passing a current of say 25 A through the circuit. There must be some rationale of doing it this way somewhere. I can't answer that question. But, I can provide you with data that says that the production-line 25-amp test is no better than a simple continuity test. See: http://www.ewh.ieee.org/soc/emcs/pstc/psn/ Then, view the following files: 97V10n1.pdf 97v10n2.pdf In each document, turn to Technically Speaking. For more than you ever wanted to know about grounding, including the 0.1 ohm value, see: http://www.ewh.ieee.org/soc/emcs/pstc/tech-spk.htm Then click on: Equipotentiality and Grounding (PDF 118K) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: North American Production-Line Tests; ANSI or Other
Hi Peter: Anyone knows of ANSI or other North American production-line test procedures/requirements for electrical/electronic equipment? Some UL and CSA standards specify the procedures for roduction-line tests, but what I am looking for is the source of these procedures/requirements. I don't believe any North American standard specifies production-line tests. For UL, production-line tests are specified in the front of each Volume of the UL Follow-Up Services (FUS) procedure. For CSA, I believe production-line tests are specified in the product report. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Defamation
A message was posted that defamed another subscriber. That subscriber has been un-subscribed and notified as to the reason. Richard Nute Administrator, IEEE emc-pstc listserver This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Violation of IEEE emc-pstc advertising rule
A message was posted by the EMC Compliance Management Group that was a blatant violation of our rules against advertising. The subscriber has been un-subscribed and notified as to the reason. Richard Nute Administrator, IEEE emc-pstc listserver This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)
Hi Peter: My comments were based on the proposed requirement to test the PE path with the circuit prospective current transient, e.g. 200 amps from a 10,000-amp source for the period of time required to operate the overcurrent device -- say less than a second or so. (The 200 amps is a function of the contact resistances and the wire resistances, independent of the fault; the duration is a function of the overcurrent device. 200 amps is a reasonable number for plug-and-socket cord-connected products.) In order to get this maximum current, the fault must be near zero ohms for the duration of the current transient. To achieve near-zero ohms, the fault must be a large- area fault. A small-area fault is likely to fuse open due to the current density and resistance at the contact. (I had the unfortunate experience that such a test by a cert house used a small-area contact at a point where no basic insulation fault could occur; the PWB PE path was destroyed. We repeated the test at a large-area contact where basic insulation could fault, and the PWB PE path passed.) What if the over current device operates, the earthing path is compromised by the fault, but not destroyed? I believe this is the objective of the proposal -- to test the PE path with the circuit prospective current. I would expect the compliance criterion to be no damage to the PE path. What if the fault is of nonnear-zero impedance, the earthing path is damaged, but not opened, and resetting of the breaker does occur, but at some point the breaker holds due to the relatively high impedance? This scenario moves from withstanding the circuit prospective current to withstanding the steady-state current just below the operating point of the over- current device. I suggest that this is the objective of the existing requirement to test at twice the overcurrent device rating or 25 amps, whichever is less. a relatively complex earthing path, I have prepared a separate e-mail that includes some construction details and empirical data for a product in my lab. To be sent soon. I appreciate you sharing this data. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Unity power factor
Hi Neil: All I get on visiting the site is 404 Page not found error on their home page. Access to all other pages seems to be ok. Using their search engine facility does not seem to find anything with respect to application notes or harmonics. Anyone else have this problem? Sorry about the bad reference. Try: http://www.fluke.com/ElectricalPower/El ctrical_register.asp?AGID=3SID=103redir=/electricalpower/appnotes.asp If this doesn't work, go to the home page: http://www.fluke.com/ Then, just work your way through the site until you find electrical power application notes. The title of the app note is: In Tune with Power Harmonics. Good luck and best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)
Hi Peter: Not quite. I^2·t will tell you the let through current of the copper trace, but will not necessarily tell you if the construction will be compliant. The compliance criteria for this test include: * no damage to the trace (no lifting, probably no discoloration) * no damage to the PWB (no delamination, burning; I don't know if this includes burning off of solder mask) * before and after earthing impedance must comply with the 0.1 Ohm maximum impedance * no change in earthing impedance greater than 10% of the before and after earthing impedance results This test implies a near 0-ohm fault to the PE, where the PE circuit includes a PE trace on the PWB. If there is a zero-ohm fault, an over-current device, somewhere, will operate. (Indeed, this is the function of the PE circuit!) A zero-ohm fault implies a large-area contact with a fair amount of contact pressure for at least the period of time to operate the overcurrent device. (A point-contact fault would blow a hole in the copper trace due to very high current density at the point of contact.) Consequently, the product must be removed from service and repaired before being returned to service. If the 0-ohm fault is on the PWB, then the PWB will need to be replaced. It is difficult to imagine a fault of 0-ohm proportions that could be repaired without replacing the PWB assembly. Indeed, if the PWB PE circuit carries the high transient current, it may very well be that the supply conductors on the PWB may be blown off the PWB. So, I question whether the compliance criteria need be applied. There is also the much more variable solder in the earthing path. While manufacturing techniques have come a long way in terms of consistency, the amount of solder in a joint and the quality of the joint itself can play a significant role. It should be expected that a lower melting point solder will perform less well than a higher melting point solder. Appropriate process controls will have a positive effect. An ideal solder joint involves an amalgam at the joint with the conductors. The properties of the amalgam are typically greater than the property of either material alone. As in copper plumbing joints, an idea joint has very little solder between the two components being joined. My guess would be that the current path will be that of least resistance, which will minimize the current through the solder around the joint. So, I would doubt that the solder (of a good joint) would be much affected by the current pulse. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)
Hi Chris: It seems funny to me that most equipment has been historically made with 18AWG protective ground pigtail wires; and 25A ground fault tests have been used for years. Now that PC traces are being used for protective ground; we want to test with 200A or greater impulse currents? I'm curious about what would happen to your typical 18AWG line cord during this test. I'm wondering if the line cord would fuse open? The 18 AWG readily passes the circuit prospective current test. This is because the current is transient, and is cut off before the wire in the cord can reach fusing temperature. One is at www.kepcopower.com/nomovax2.htm this is a nomograph of maximum operating current, AWG and IR drop in the conductor. The point A is generally considered the point of maximum IR drop. If you draw a line from point A, through a wire gauge size; you'll get a max current. Of course this is steady state current; and the nomograph assumes a single wire. Wire bundles would be a worse case. It's too bad that this chart doesn't contain the fuse values for the wires as well (the I squared * T values). Fusing currents for wires are published in: Reference Data for Radio Engineers International Telephone and Telegraph Corporation 67 Broad Street New York 4, New York This reference says Courtesy of Automatic Electric Company, Chicago, Illinois. The approximate fusing current for 18 AWG copper is 82.9 amperes. The approximate fusing current of wires can be calculated from: I = (K) * (d**3/2) where d is the diameter of the wire, in inches K is a constant that depends on the metal Here are some values for K: copper:10,244 aluminum: 7,585 silver: 5,230 iron: 3,148 tin:1,642 The Standard Handbook for Electrical Engineers by Fink and Beatty has some additional data, including curves of current and time for each AWG. A couple of points for 18 AWG: 0.1 second:~720 amps 1.0 second:~220 amps 10.0 second:~ 82 amps 3. The third problem is mechanical. Once Earth ground brought to a pad on the circuitboard; then there is still the issue of getting a good mechanical mate to the chassis with a wide surface area. If the connection is made through a couple of teeth on a star washer; then there is a potential for localized heating. I'm just going to maximize surface contact area for this one. I'm also considering using multiple board to chassis connection locations. Every screw that connects the board to chassis is a potential Earth ground connection. The problem with mechanical connections to PWBs by means of screws is that the PWB base material is a plastic and is subject to cold-flow under compressive conditions. In the long-term, the connection can loosen. Not everyone pays attention to this, and, in practice, it is rarely a problem. One way around this is to use a wire from the board to the chassis. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN60950 protective conductor test
Hi John: Is it not permitted to express a personal preference on this group? I *prefer, personally*, not to use printed board traces as parts of the PEC. I'm not suggesting that should be in IEC 60950 or any other standard. Of course we express personal preferences in this group! Almost every message is a personal preference. :-) The point of my message is to argue against your personal preference as there is nothing inherently wrong with PWB traces as part of the PE circuit. Some SMPS use a grounded heat sink -- on the PWB -- for the switching transistors. In this case, the electrical circuit path from the heat sink to the earth terminal of the IEC 60320 connector is a part of the PE circuit, and must be capable of carrying the fault current. Running a wire from the heat sink to the terminal is a manual job, and introduces two connections that are operator- dependent whereas the PWB connections are not. Another point... which I hesitate to mention... is that, while Y2 capacitors require connection to a PE return, some test houses require a PE return for Y1 capacitors! In my experience, PWB PE circuits are common, and most difficult to obviate. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EN60950 protective conductor test
This message has been converted via the evaluation version of Transend Migrator. Use beyond the trial period specified in your Software Evaluation Agreement is prohibited. Please contact Transend Corporation at (650) 324-5370 or sales.i...@transend.com to obtain a license suitable for use in a production environment. Thank you. br -br Hi John: short-circuit conditions. The printed-board mounting versions of the IEC 60320 appliance connector encourage the use of board traces to carry the PEC; something that I would not be happy about, in principle. Such construction cannot be sloughed off in such an off-hand manner. This is solo BOGSAT engineering, which cannot be condoned. Rather, the scientific method must be applied so as to reach a conclusion that has a foundation supporting the conclusion. 1. Statement of the problem. Board traces to a board-mounted IEC 60320 applicance connector cannot withstand the prospective short-circuit current. 2. Hypothesis as to the cause of the problem. The cross-sectional area of the connection from the board trace to the 60320 connector is insufficient to withstand the prospective short-circuit current. 3. Experiments designed to test the hypothesis. Design a set of boards with different cross-sectional areas of the connection of the board to the 60320 connector. Apply the test to each board. 4. Predicted results of the experiments. Where the cross-sectional area equals or exceeds that of the supply conductors, the connection will not fail. 5. Observed results of the experiments. TBD 6. Conclusions of the experiments. TBD The real purpose of the scientific method is to make sure that Nature hasn't misled you into thinking you know something you don't actually know. -- Robert M. Persig, Zen and the Art of Motorcycle Maintenance. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Unity Power Factor
Hi John: Thank you for that and the rest of the information, which could prove to be very helpful indeed. I would like to use it in my continuing efforts to defuse the arguments between the former TC74 experts in TC108 and the SC77A/WG1 people. May I say that the information came from you (personally, of course, not from HP)? Fluke has a good explanation of the deleterious effects of harmonics. See: http://www.fluke.com/ElectricPower/elec.asp Click on Application Notes. This will take you to a registration page which you must complete before you can get to the App Note. After registering, click on In tune with harmonics. This App Note covers a number of effects of harmonic currents that I have not discussed. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Unity Power Factor
Hi John: Yes, delta-wye distribution transformer overheating does occur due to the circulation and dissipation of the triplen harmonics in the primary (delta) winding. Thank you for that and the rest of the information, which could prove to be very helpful indeed. I would like to use it in my continuing efforts to defuse the arguments between the former TC74 experts in TC108 and the SC77A/WG1 people. May I say that the information came from you (personally, of course, not from HP)? Actually, I learned this and other facts about harmonics from my participation, some years ago, in the CBEMA (now ITIC) ESC-3 committee. The minutes of those meetings (whereever they may be) would support my assertions. My understanding of the European situation is that up to 600 homes could be on one distribution transformer, and that the power is distributed as three phases with one neutral. The cumulation of harmonics on such a system would indeed tend to flat-top the voltage waveform for those homes that are far from the transformer. Also, the harmonics would tend to overheat the primary of the distribution transformer, the failure of which would cause a much larger outage than in North America. Likewise, in Europe, within commercial and industrial sites, the distribution transformer is comparatively large, and supplies a very much greater load. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: single fault conditions
Hi John: The Bad: some FETs fail very violently, and can actually be a fire hazard and/or shock hazard in open-frame switchers; Really? There doesn't seem to be enough combustible material to cause a fire hazard, and an open-frame switcher always has to be in some sort of outer enclosure, doesn't it? So it's not clear how a shock hazard could arise. In the case of switching FETs, the power dissipated in the FET resistance can raise the encapsulent material to ignition temperature in which case it will burn until consumed or until the power to the FET is cut off. (While the encapsulent material is flame-retardant, flame-retardant materials burn as long as thermal energy is applied to the material.) Depending on the specific construction, the flame from the burning encapsulent material could ignite nearby materials. However, the standards do not allow non-flame-retardant material near mains circuits and, ipso facto, near switching FETs. The thermal energy from an overheated switching FET may damage basic insulation -- such as the insulation between the FET and its heat sink. Heat sinks are either connected to one side of the mains, or are connected to ground. If connected to ground, the connection should meet the requirements for a protective ground. So, the failure of switching FETs could give rise to both fire and shock, but should not do so if the equipment construction is according to our various safety standards. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: single fault conditions
While s-c and o-c at device terminals do not simulate true fault conditions within components, testing must be practical. If we are to begin considering simulation of true fault conditions within components, there may be no end to the number of tests. We can easily put bounds on the number of fault-condition tests. First, there are no fault-condition tests for electric shock. The requirements for electric shock presume the failure of basic insulation, so we do not need to fault basic insulation. Second, fire only occurs under fault conditions (a priori). So, we need to introduce those faults likely to cause heating sufficient to raise a fuel material to ignition temperature. Electrical heating occurs in a resistance. So, the faults that should be introduced are those that will produce maximum heating in a specific resistance for a prolonged period of time. This premise requires identification of resistances capable of dissipating enough power for a long enough period of time for ignition of nearby materials. Once this is done, then the faults that are considered are those that will maximize current in the resistances. This process narrows down the number of fault tests to a very reasonable number. (By the way, this process is no different than that for fault testing x-radiation from crts -- only those faults which will maximize the anode voltage are considered.) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Unity Power Factor
Hi John: Aren't you in the USA? If so, you must have imagined the peak- flattening. I am assured by the US experts on SC77A/WG1 that this phenomenon is unknown in USA, and the only effect of IEC/EN 61000-3-2 is that it increases the prices of PCs dramatically and keeps US products out of Europe. To which my answer is 'McEnroe!' (YCNBS!) At least, they argued that way for about 10 years. The present US chums are far more sensible. Even so, 'peak flattening' rarely figures in their vocabulary. As Ken Javor described, in the USA, voltage distortion is largely a local (privately-owned wiring) premises problem due to excessive series resistance between the load and the point where the utility connects to the local premises wiring. Voltage distortion at the point where the utility (public network) connects to the local premises wiring is rare. As mentioned in another message, the effect of non-linear loads (in the USA) on the utility (public) network is very low due to our use of many small distribution transformers as compared to the large distribution transformers used in Europe. The effects of non-linear loads in the USA are highly localized, and, in commercial and industrial sites, tend to be owned by the site owner. Voltage distortion on utility (public) networks in the USA tends to occur near sites of aluminum smelting and electric blast furnaces. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: single fault conditions
Hi Brian: The environment being considered is a switching power supply. The technique that safety agencies use to simulate a SFC on a power FET does not seem, IMHO, to simulate the actual failure mode of the device. To wit: when the mosfet fails short, it blows itself open; so the amount of current sucked out of mains, e.g., the PFC FET, would probably open the component after a few input cycles. But if I apply a direct mechanical short (source to drain), current is being forced to flow until the fuse blows, or until some series trace or component opens. The shorting of a component does not test that component. Instead it tests the remainder of the circuit for (safety?) weaknesses in the event of a short (or near-short) of that component. I suppose the opening of a circuit does test for the component failing in the open condition. But, the effect of the open-circuit is to test the remainder of the circuit for (safety?) weaknesses. So, shorting or opening of a component does not test the component but other parts of the circuit. In general, the termination of fault tests should be not only repeatable, but should be understood so that the parameters that make the termination repeatable are under control. The operation of a fuse is a good termination of a fault test. A cascaded fault of another component may not be a good termination of a fault test because the safe termination may depend on unknown or uncontrolled component characteristics. The Bad: some FETs fail very violently, and can actually be a fire hazard and/or shock hazard in open-frame switchers; but if the FET itself does not provide the short circuit, we will never know Switchers generally drive the switching FETs with a pulse-width-modulated waveform. One way to introduce a fault that tests the FET is to simulate a 100% duty cycle pulse by applying a dc voltage of the same voltage as the PWM signal. This will turn on the FET continuously, and you should get your spectacular failure. The Good: providing a continuous (mechanical) short will reveal if there are other components in the current path that could be cause the unit to fail in an unsafe mode. Although, according to QA records, these components have never failed, so it can be both demonstrated by design equations and empirical evidence that the SFC test does necessarily demonstrate anything relevant... Uh, no... I don't think you want to base your fault-condition safety on empirical data that the fault will not occur. I have never seen the fault of basic insulation in the field, but we nevertheless account for the failure of basic insulation with either grounding or supplemental insulation. There is nothing like a test. The Ugly: Safety testing results in design corrections that do not increase product safety. I would argue this point. I have not seen undue design corrections due to a fault test. So would it be legitimate to over-drive the gate, forcing short circuit current to flow through the FET, but not to apply a mechanical short across the component? Yes! But, unfortunately, some components do not lend themselves for such testing. Capacitors are a good example -- almost impossible to induce a fault. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Unity Power Factor
Hi John: The only other problem that I know of is distribution transformer overheating. But, I believe such transformers are very much larger than 3 kVA, so 3 kVA of non-linear loads would have very little effect. I mean *concentrations* of loads, individually below 3 kVA or so. Distribution transformer overheating is the sort of effect that I am interested in. Are these MV/LV transformers, 'pole-pig' types or larger. Yes, delta-wye distribution transformer overheating does occur due to the circulation and dissipation of the triplen harmonics in the primary (delta) winding. As for the type of transformer, it is the first three- phase transformer upstream from a commercial or industrial load. (In North America, these transformers are relatively small compared to Euro practice.) Such transformers are usually a part of the (larger) customer premises wiring and installation, and are not a part of the public utility distribution system. So, harmonics in commercial/industrial equipment do not appear on the public network. In North America, this overheating problem due to triplen harmonics has largely disappeared with the advent of the distribution transformer K-factor rating that was developed especially for this problem. By contrast, homes in North America a supplied with single-phase from a single-phase distribution transformer (which is connected across two legs of a three-phase delta supply). So, harmonics in home equipment do not appear on the public network. (Each distribution transformer supplies a maximum of 8 homes, each with 200-amp service.) In addition to overheating neutrals, some manufacturers of partitions (for office cubes -- cube sweet cube!) included three-phase wiring. The neutral connection of partition-to-partition connectors tended to overheat due to harmonics, and several fires were reported. These, too, were fixed (I believe by doubling the neutral or the neutral connection). Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Unity Power Factor
Hi John: In the USA, this has largely been fixed by a change in the USA National Electrical Code. There must be quite a number of installations that are not yet upgraded. Where a problem existed, it was fixed by pulling another neutral. Are there any other problems appearing in the field which can be reliably determined as due to concentrations of non-linear loads of less than 3 kVA or so? Probably not. The only other problem that I know of is distribution transformer overheating. But, I believe such transformers are very much larger than 3 kVA, so 3 kVA of non-linear loads would have very little effect. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Circuit Breaker Tripping Dring Fault Tests
Hi Peter: For safety, it is not clear from the standards whether the main branch circuit breaker tripping during fault conditions is an acceptable result. I see no reason why this should not be acceptable. What is your view? Some third party labs find it acceptable and others do not. Some products are provided with internal overcurrent protection and some are not. Clearly, those that do not have internal overcurrent protection rely on the branch circuit protection. If a product has an internal overcurrent protective device, and the fault is on the load side of that device, then the internal device should provide the protection and not the branch circuit device. (Otherwise, the internal device provides no protection, and might as well be removed.) If the fault is on the supply side of the internal device, then clearly the internal device cannot provide protection, and the branch circuit must provide the protection. The real question is whether or not the product is safe when the fault current is just below the operating point of the branch circuit device. Examining this question requires an understanding of the fault and whether its resistance can be high enough to not trip the branch circuit yet not create a hazardous condition (such as a fire). If the fault resistance always is no more than 120/20 = 6 ohms, then I would say that the branch circuit could be relied upon to provide protection against the fault. Note that in the USA, a 120-volt branch circuit can be provided with either a 15-amp or a 20-amp overcurrent device. Therefore, the product must be safe when the fault current is 20 amps, just below the overcurrent device operating point. That means that the product must be capable of dissipating 2400 watts without catching fire or destroying internal insulation that serves a safety purpose. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Unity Power Factor
Hi John: No, this is not much of an issue for the U.S. (unless your facility is actually affecting the utility); ... or frying the neutral conductors with third-harmonic current. In the USA, this has largely been fixed by a change in the USA National Electrical Code. When the load is largely electronic (off-line rectifiers) the Code now requires a larger neutral conductor in three- phase distributions. Many constructions, while supplied from a three-phase source, are wired as single-phase. So, in this case, the neutral only carries the current of one phase, and we don't fry the neutral. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Listserver Administrative Notice
Listserver Administrative Notices: 1. No attachments. --- Please do not post messages with attachments. We have a large number of subscribers on plain old telephone dial-up service. Messages with attachments take a long time to download, and the download can be interrupted, which means downloading again. Here are some alternatives for attachments: a) Post the attachment to our new web-site: http://www.ieeecommunities.org/emc-pstc (See item 4 for joining instructions) b) Offer to send the attachment upon private request. c) Make the file available on an anonymous ftp site. 2. Plain text. --- Please post messages in plain ASCII text. (This message is in plain ASCII text. If your posted message looks different than this message, then you probably are not posting in plain text.) We have subscribers all over the world using all sorts of different mail applications. When text is not plain text, some mail applications cannot properly display the text, and the message may appear garbled (although usually readable). Set your mail application to send messages to our listserver in plain text. If you use Outlook: a) Click on Tools in the top toolbar. b) Click on Options. c) Select Mail Format tab. d) Send in this message format select plain text. This will send ALL outgoing message in plain text. If you don't want all outgoing messages in plain text, then: a) Open your Address Book. b) Select the listserver address, and double- click. c) Select the SMPT-Address tab. d) Uncheck the Always send to this recipient in Microsoft Outlook rich-text format. Other mail applications will likewise have a means for sending messages in plain text. 3. Archives. - Our new web site is not yet set up to handle our message archive. We're working with the site provider to get this feature added. Sorry, but we don't have a date for completion of this project. Our new web site is: http://www.ieeecommunities.org/emc-pstc 4. Our new web site. - If you want to use our new web site, you will need to join the web site. Go to: http://www.ieeecommunities.org/ On the left side of the window, click on Application and follow the instructions. Thank you for your cooperation. If you have any questions or comments, please reply to me and/or the other administrators, not to the listserver. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
jurisdiction, overlap, and delegation in USA rules.
Hi John: The electrical safety legislation seems to be a bit more complicated in U.S. compared to EU. A very great deal more complicated, because the practical requirements are not centralized but delegated down though the local government chain, and in some cases jurisdictions overlap or are not clearly segregated. I'm not at all sure what you mean by the practical requirements are not centralized Furthermore, in the USA, requirements are NOT delegated down though the local government chain Furthermore, there are NO cases where jurisdictions overlap or are not clearly segregated. Depending on the State, building codes are set and enforced by either the State, the County, or the City. These are the jurisdictions. There is no jurisdictional overlap or lack of clear segregation (at least insofar as building codes are concerned). Within the Building Code, there is a subset, the Electrical Code. These Codes comprise a Standard for the construction of buildings, including the electrical construction of the of the building. Electrical codes typically require the individual materials used in the electrical construction, including appliances, to be certified for safety (Listed) by safety labs specified in the local code. There is no delegation down through local governments. The USA Federal government Department of Labor has a separate and independent (from building codes) set of safety rules for employees. One of the rules addresses electrical safety in the workplace. Included in these electrical safety rules is a rule specifying that the electrical equipment used by employees be Listed (by a NRTL). A jurisidictional overlap may APPEAR to exist between the electrical code and the DoL OSHA rule. However, in practice, both organizations have been very careful not to tread in the other's jurisdiction. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: NRTL in the U.S.
Hi Gregg: I argue with some of your statements. :-) Dave's question - Does this apply to in-house test equipment? Hi Dave - Good question (Please see attached). I'm sorry about the file size but I took it from the Department of Labor web site several years ago when this topic first came up. (It repeats about every 6 months if my memory serves) I believe Dave's question was in regard to compliance to local electrical codes, not to OSHA requirements. Local electrical codes (e.g., NEC) require all electrical equipment that comprises an electrical installation to be approved for the purpose. This is taken to mean listed or otherwise certified for safety. Codes are enforced by local inspectors and by licensed electricians who perform the installation. Department of Labor (OSHA) regulations require that the electrical equipment used by employees be certified for safety by an NRTL. Regulations are enforced by the employer as well as by periodically by inspectors from OSHA. While these two sets of rules are independent of each other, one solution satisfies both rules: listing. However - the BEST and MOST RELEVANT people to ask are your Corporate Insurers. It would be little good meeting the local code to find that there is small print in your corporate liability insurance leaves you with personal liability for any failure - injury or death!!! Even if you can avoid NRTL testing then you need to protect yourself - NOT YOUR COMPANY - (people go to jail - companies don't). As a general rule, employees cannot be held personally liable if they are doing work in accordance with direction from the employer. But, today's focus on profits motivates many insurers to creatively find a way to prevent payment of claims or to recover the loss from some other source. However, recovering from the likes of you and me would not come close to covering the loss. There are bigger fish and deeper pockets. Try to think of 'compliance' not as PASS or FAIL; but as a continuum from DEPLORABLE through ACCEPTABLE to the UNATTAINABLE. These abstractions, DEPLORABLE, ACCEPTABLE, and UNATTAINABLE, are difficult to use because they are not very measurable. PASS and FAIL at least provide a line by which to discriminate between acceptable and unacceptable. We, at HP and Agilent, use a three-block model to evaluate safety: +-++-++-+ |hazardous|| || | |energy |---|safeguard|---| body | |source || || | +-++-++-+ We say that, for every hazardous energy source, there must be one or more safeguards interposed between the source and the body. The safeguard has a number of parameters that must be controlled such that the safeguard remains effective for the equipment lifetime. If we do a thorough job, then we have a safe product -- unless the safeguard is subjected to influences greater than the design level. This is a practical, powerful, and measurable model for safety. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: NRTL in the U.S.
Hi Gary: Rich Nute (I think) wrote and excellent article or e-mail on this not too long ago and should be in the archives. Its pretty concise and clear but goes into some pretty good specifics and the state laws and how they very and you will find it very helpful. Unfortunately, the archives are not available at this time due to our web site transition from Akiva to Community Zero. We hope to have the archives available in another month or so. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: NRTL in the U.S.
Hi Dave: Does this apply to in-house test equipment? That is, equipment that is built in-house and remains on site? In the past I have designed in-house equipment to meet the safety standards but did not send the equipment out for testing and certification. Yes. If you check with your local electrical code inspectors (or, if you have one, your in-house electrician ), you will find that custom-built equipment used in your factory or site must meet the electrical code, which means it must be certified for safety. Many of the certification houses offer on-site investigations of such equipment. UL has a standard (I don't recall the number) for such equipment. Upon successful completion of the investigation, the cert house will put a sticker on the equipment, and the electrical code inspector will accept the equipment. (Such certification also protects your employer against violation of OSHA rules.) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: NRTL in the U.S.
Hi Joe: As has been discussed in previous threads, NRTL Listing is not a requirement to sell electronic products in the U.S. However, there are cities, counties, etc. within the U.S. that do require NRTL Listing. These include Los Angeles and Chicago. Does anyone have a comprehensive list of all the cities, counties or states that do require NRTL Listing. The list would be very much shorter if the list contained those cities or counties that do NOT require safety certification. (I would venture to say there are none.) You could probably get such a list from UL or CSA or MET or ETL other safety certification house that has applied for and been accepted in those jurisdictions. Just ask for a list of states, counties, and cities where their mark is accepted. Personally, I know of no city, county, or state that does not require safety certification (listing) of electrical products. Your mention of cities, counties, and states implies the local electrical code requirements (usually the NEC). NRTL is a concept of the Occupational Safety and Health Adminstration (OSHA). OSHA is a federal government entity that addresses workplace safety, not local electrical codes. NRTL certification of an electrical product used in the workplace satisfies an employer's requirement (under OSHA) to supply a safe electrical device for use by employees. There is no connection between local electrical codes and NRTL. But, we know what you mean! :-) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Alternatives to Brominated Fire Retardants
Hi Richard: Does anyone know of web sites or other sources that describe feasible alternatives to bominated fire retardants in plastics? There are a number of alternatives to brominated fire retardants: Phosphorus Mineral Phosphorus is probably the most-used. There are some other up-and-coming fire retardants, one of which, I believe, is sand (or silicon). You might try: www.polymeradditives.com to get an idea of the various fire retardant additives and manufacturers. Or, you can buy a good book on flame-retardants: International Plastics Flammability Handbook by Jurgen Troitzsch Hanser Publishers ISBN 3-446-15156-7 Carl Hanser Verlag, Munich ISBN 0-19-520797-1 Oxford University Press, New York Finally, check out: www.albermarle.com/saytexbrochf.htm This web site discusses some of the hazardous products of combustion from various brominated fire retardants. This web site may not be impartial. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: strange symbols (to me anyway)
Hi Gary: As a result of searching for my copy of the indoor use only symbol, I discovered that I have a reference to the standard where the symbol is published: DIN 30 600 Reg. No. 02808-3 If one of our subscribers has a copy of this standard, perhaps he could verify the reference. If possible, I'd like a copy of the page that describes this symbol. (Or, we could post the copy to our new emc- pstc web site for all to see.) Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: strange symbols (to me anyway)
Hi John: It is not an ISO or IEC symbol. It is either in IEC60417 already or will be in the future. It is not currently in IEC 60417. (I have no visibility as to future adoption of this symbol into IEC 60417.) Since one of our members could not decipher the symbol, I question the value of the symbol to laymen and therefore its inclusion in IEC 60417. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
comment worth a further look
Hi Luke: This won't work. If you want to look at how badly online forums work, look at the IEE website. Unfortunately, this requires a membership and a login. I really would like to know more about the success of web-based forums. Best regards, Rich
The listserver WILL continue.
Thank you for all the comments on the listserver- based service versus the web-based service. The IEEE listserver WILL continue. I apologize for not being clear on this point. We started with listserver service. However, the listserver does not satisfy all of the needs of our subscribers. So, we supplement the listserver with a web service. Some of our supplemental needs: 1. Archive of listserver messages, with a search function. 2. A means for providing papers that cannot be sent via the listserver due to size limitations. 3. A means for announcing local chapter activities without sending the notice worldwide. 4. A means for selective messaging (to eliminate non-pertinent messages from your inbox). 5. A means for providing papers of both general interest and highly-specialized interest. 6. A means for reporting IEEE EMC Society and emerging Product Safety Society activity. 7. A means for threaded discussions. etc. The ideal scheme would include all of this in a single integrated scheme. As explained in my previous message, for the moment we do not have this capability. Both the listserver service and the web-based service provide discussions. Therein lies the problem: Two discussion groups, with no connection between them. The listserver discussions are readily transmitted over all forms of connections. The web-based discussions are largely impractical for slow (telephone) connections. We recognize this. For the moment, we have two discussion services. Your usage of each will influence how we will resolve the two discussions into one. Or maybe, separate, user-selectable discussions based on our broad topics of EMC, safety, telecom, wireless, etc. I welcome your comments and suggestions! Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Death of the listserver
Hi Jim: Thanks for your message. The EMC Laboratory that I work for (Acme Testing Company in Acme, Washington) has the quietest open-field Emissions Sites (OATS) within a 1000 mile radius. We planned it that way. The village of Acme has a total population of under 100 people. My home in Glacier, WA (five miles from the Canadian border) has a population of 90. Cable and telephone companies do not run underground cable for 90 people. Cable or broadband Internet is a wetdream that will never happen here. It's 56k ... or nothing. I find this daily interchange of EMC-related topics to be very important in my work. I will miss it if the participation dwindles. Our intent is to provide more and better service to our subscribers. A few years ago, we surveyed our listserver subscribers. One big feedback item was that many subscribers did not want to get all of the messages, but only those that were in their line of interest. Two years ago, the IEEE engaged Mindcruiser to help them set up e-communities. EMC-PSTC was invited to participate as we have nearly what the IEEE envisioned as an e-community. Mindcruiser would support selective e-mail distribution of messages. Jim and I and the IEEE worked with Mindcruiser to set up an e-community web site. Jim and I insisted that the Mindcruiser site support the listserver function. Mindcruiser developed a listserver support function that worked, but we had a number of other problems with Mindcruiser as did the IEEE. So, the IEEE discontinued their contract with Mindcruiser and changed to Community Zero, who already had a functioning e-community web application. Community Zero met the IEEE needs, but does not and will not support a listserver function. Your feedback is important to us. Clearly, the C-Zero web-based e-community does not meet all of our subscriber needs. At the moment, we are looking at two, separate schemes. One is web-based. The other is listserver based. The web-based scheme can notify the listserver subscribers of items posted on the web site. But, it does not work the other way around. We won't sacrifice our function to meet the IEEE needs. Whatever scheme the IEEE arrives at, it will not drive us to satisfy the scheme versus satisfying our subscribers. Best wishes for the New Year! Rich From owner-emc-p...@majordomo.ieee.org Wed Jan 1 20:33:36 PST 2003 Received: from sanrel1.sdd.hp.com (sanrel1.sdd.hp.com [15.80.36.45]) by hpsdlfsa.sdd.hp.com (8.9.3 (PHNE_18546)/8.9.3 SMKit7.02 sdd epg) with ESMTP id UAA09662 for ri...@hpsdlfsa.sdd.hp.com; Wed, 1 Jan 2003 20:33:35 -0800 (PST) Received: by sanrel1.sdd.hp.com (Postfix) id 858359717; Wed, 1 Jan 2003 20:33:35 -0800 (PST) Received: from localhost.sdd.hp.com (unknown [127.0.0.1]) by sanrel1.sdd.hp.com (Postfix) with SMTP id DF80796A9 for ri...@sdd.hp.com; Wed, 1 Jan 2003 20:33:32 -0800 (PST) Received: from ruebert.ieee.org (ruebert.ieee.org [140.98.193.10]) by sanrel1.sdd.hp.com (Postfix) with ESMTP id 2F63C9717 for ri...@sdd.hp.com; Wed, 1 Jan 2003 20:33:31 -0800 (PST) Received: (from daemon@localhost) by ruebert.ieee.org (Switch-2.2.4/Switch-2.2.4) id h021pAU20093 for emc-pstc-resent; Wed, 1 Jan 2003 20:51:10 -0500 (EST) Message-ID: 002601c2b201$54c05f00$98663fce@pavilion From: Jim Ericson jde...@nas.com To: emcpost emc-p...@majordomo.ieee.org Cc: Harry Hodes hhho...@yahoo.com Subject: Death of the listserver Date: Wed, 1 Jan 2003 17:50:25 -0800 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Sender: owner-emc-p...@majordomo.ieee.org Precedence: bulk Reply-To: Jim Ericson jde...@nas.com X-Resent-To: Multiple Recipients emc-p...@majordomo.ieee.org X-Listname: emc-pstc X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org Dear Richard and Jim [co-administrators]: The EMC Laboratory that I work for (Acme Testing Company in Acme, Washington) has the quietest open-field Emissions Sites (OATS) within a 1000 mile radius. We planned it that way. The village of Acme has a total population of under 100 people. My home in Glacier, WA (five miles from the Canadian border) has a population of 90. Cable and telephone companies do not run underground cable for 90 people. Cable or broadband Internet is a wetdream that will never happen here. It's 56k ... or nothing. I find this daily interchange of EMC-related topics to be very important in my work. I will miss it if the participation dwindles. Regards,
Re: Leakage current test conundrum
Hi Charles: a) Does anyone one know the genesis of the requirement to lift the Neutral AND the Ground simultaneously during a leakage current test?? (I am referring to UL6500) While I am not familiar with UL 6500 per se, I believe I can comment on the lift of the neutral. In times past, non-polarized products used a single-pole power switch. Since the products were non-polarized, the single-pole power switch could be in the neutral rather than in the phase conductor. When the switch is in the neutral and is open, the leakage current essentially doubles compared to the value when the switch is closed (assuming the switch is ahead of the line filter). (Draw the circuit and you can readily see why the leakage current doubles.) Certainly, leakage current should be measured (and controlled) for both the ON and OFF positions of a power switch, especially a single-pole power switch. b) What human body model is appropriate for UL6500? Can I use the one in UL1950?? Since you are referencing UL standards, the correct measuring circuit (i.e, human model) is the ANSI circuit (C39.5?). In practice, just use an ordinary ammeter. This will give you a slightly (~5%) pessimistic measurement. So, unless you are very close to the leakage current limit, you need not use the humand body model for leakage current measurements. For more details on both these questions, see my article in the Product Safety Newsletter, Volume 7, Number 1, January-February 1994. You can download a pdf version of this PSN: http://www.ewh.ieee.org/soc/emcs/pstc/psn/ The file name is: 94v07n1.pdf Best regards, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Methenamine timed burning tablet
Some fire tests use a methenamine timed burning tablet. This tablet is specified in USA government standards for furniture flammablity testing. (See 16 CFR Part 1630.4 or CPSC standard FF 1-70.) It is also specified in ASTM D2859. I have also seen it used to test fire enclosures in Europe. Until February of this year, Eli Lilly supplied this tablet as Catalog No. 1588. In February, 2002, Eli Lilly discontinued the tablet. According to Eli Lilly, no other US manufacturer has picked up this tablet; they did not know if a Euro manufacturer was making the tablet. I am looking for a source for this methenamine tablet. If you can provide some pointers, I would appreciate it. Thanks, and best regards from San Diego, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Administrative message -- posting formats
Regarding postings, here is a re-statement of our guidelines that were sent to you when you subscribed: 1. No attachments (because many of our subscribers use dial-up modems for which message size determines the download time). If an attachment is appropriate or necessary to your message, then a) offer to e-mail it separately upon request, or b) make it available on an FTP site, or c) post it to a web site and provide the URL in your message. 2. Post in ASCII plain text. Do not use RTF, HTML, or similar formats. Not all mail readers are compatible with these formats, but all mail readers are compatible with ASCII plain text. In most cases (especially Outlook), you can set your mailer to always use ASCII plain text for messages sent to emc-pstc. Also, please don't write messages without carriage returns. Some mailer readers can't handle long lines, so the line is truncated and part of the line disappears. If you use CR (ENTER) at the end of each line, then each reader will see the same format as the one you wrote. 3. Please don't re-post the entire message string when replying to a message. Instead, pick out the passages to which you want to respond, enter your response, and delete the other text. This makes your point easier to understand, and helps keep the message size down for our modem- connected colleagues. Don't forget to delete the emc-pstc footer! :-) (Each posted message gets the footer attached; multiple footers provide no useful information, and just make downloads longer.) 4. If appropriate, when responding to a message, change the subject line to agree with the major point or content of your contribution. You can append was 'original subject' to your subject if you want to reference the original subject. This will help us when the subject matter strays from the original. 5. If you want to attach a signature, please do so in ASCII (for the same reason as posting in ASCII), not the business card format that is gaining popularity. Best regards, Richard Nute Administrator, emc-pstc listserver Tel: +1-858-655-3329 FAX: +1-858-655-4374 e-mail: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
docopocoss
docopocoss This word was unknown to me. I checked an American dictionary and could not find it. Then, I called up the Google search engine and entered the word, hoping to find an English dictionary. Google immediately came back with the definition. Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Value of Using Non-NRTL Engineering Firms?
Hi Chris: OSHA rules apply to employers. OSHA electrical rules require employers (1) to use only electrical products that have been certified by an NRTL, or (2) in the case of custom products, to test the product in place. If you sell a non-NRTL-certified custom product to an employer who is subject to OSHA rules, then that employer must test the product in place, and file a suitable record of the testing. Few employers choose the test-in-place alternative. A listing by a non-NRTL is useless to an employer subject to OSHA rules. He can't use it for proof that the product meets OSHA rules. At the employer's discretion, you may be able to convince the employer (your customer) that your listing test report will provide a suitable record of testing to OSHA requirements. See OSHA rules, Sub-part S for complete treatment on OSHA electrical rules. See especially 1910.303(a) Approval and the respective definitions. http://www.osha.gov/pls/oshaweb/owastand.display_standard_group?p_toc_level=1p_part_number=1910p_text_version=FALSE Statement: Non-NRTL laboratories can provide Listings and publish the customers (thus Listing) however, based OSHA law, NEC requirements, Retailer specification, and other MOU/MRA with Canada/EU, it would not seem to be a significant accomplishment if not an NRTL. Except for NEC, I would agree with this statement. Best regards, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
