Invitation from ECMA/EACEM - Safety of Electronic Equipment Stand

As an inactive member of ECMA TC 12, and a TC 12 contributor for the first year of this work, I am fowarding a message from Bob Griffin, Compaq, regarding a new product safety standard for electronic equipment. Unfortunately, I am unable to include the files Bob describes. (Apparently, the lis

Re: UL 1950 Requirements for Operational Insulation

Hi Allen: > Does anyone know how to calculate minimum distances between traces on > a printed circuit board that would allow one to pass the dielectric test > at a given voltage? Or has anyone taken any empirical data that would > shed light on this topic? Also, would trace width have an impa

Re: Spacings Issue

Hi Ed: > First of all the "floating secondary ground" (if not connected > directly to earth) should be treated as part of the secondary circuit > which in many cases will require reinforced insulation to the primary > circuit according to the working voltage measured. There are t

Re: Spacings Issue

Hi Ken: See my paper on floating circuits in the Product Safety Newsletter: http://www.ewh.ieee.org/soc/emcs/pstc/tech-spk.htm This should answer all your questions. If not, please get back to me, and I'll answer any additional questions you may have. Best regards, Rich ps: Provid

Re: Risk assessment

Hi Stig: I believe you are interested in "severity of injury," not "potential for injury," or "risk of injury." Here is a numerical assignment for severity of injury that I found in my files. I have no idea of its source. 10 Death 9 Long-term or permanent coma 8 Full b

Re: Polarity Markings on AC Adapters

Hi George: > Thanks for the quick response! Does this mean that the symbology is only > a Japan requirement? and does it apply to ITE as well as > audio-visual > equipment? The referenced standard, EIAJ CP1104, is similar to IEC 417. Indeed, EIAJ CP1104 contains many s

Re: Polarity Markings on AC Adapters

Hi George: The dc polarity symbol is specified in: Symbol 01060 (taken from JEIDA 11) EIAJ CP-1104 (1998) "Terms and Grpahical Symbols for Audio and Audio-Visual Equipment" Technical Standardization Committee on Audio-Visual Equipment and Systems Electronic Industries Ass

Re: component spacing question

Hi Ken: > I wanted to pose the group a question in regards to spacing requirements for > the U.S. Many UL standards allow for the exception of components (such as > semi conductors, switches, etc) to not meet spacing requirements (as they > usually have different standards they meet

RE: TVSS Usage Restriction

David Clark pointed out an error in my posting. I SHOULD have said: According to the OSM/EE list of decisions dated 9/99... Varistors between the mains and the protective earth cannot be accepted by the following countries: Pluggable equipment, Type A: Austria, Belgium, Denmark

Re: TVSS Usage Restriction

Hi Ron: According to the OSM/EE list of decisions dated 9/99... Varistors between the mains and the protective earth cannot be accepted by the following countries: Pluggable equipment, Type A: Austria, Belgium, Denmark, Finland, Norway, Sweden, United Kingdom. Per

Re: Got a beef with an NRTL ...

Hi Doug: Your message was not clear whether you submitted your product to the same NRTL that certified the power supply. Basically, your cert engineer has put YOU in the middle of a beef between cert engineers or between cert houses. Your cert engineer found a fault in the power supply cer

For UL watchers... a job opening...

... check out: http://www.ul.com/about/newsrel/nr101300.html Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with

Re: Laser Safety Calculations

Hi George and Chris: Better still, TC76 should provide a spreadsheet such that, upon entering all the data, the spreadsheet does the calculations and gives you the emission level and the emission Class. Regards, Rich --- This message is from the I

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 > depu

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-brea

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

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 electrophore

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 Commit

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 de

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 D

Re: [PSES] UL 60950-1 clause 2.2.3

tember 08, 2014 2:42 AM > To: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] UL 60950-1 clause 2.2.3 > > In message , dated Sun, 7 > Sep 2014, Rich Nute writes: > > >I believe the authors of 60950-22 expected that user-accessible > parts > >would comprise SELV

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

Re: EMC and Class 2 equipment

Hi Amund: Being a safety guy and not an emc guy... (disclaimer) > Ground connections is usually nice to have when dealing with EMC. But what > about EMC and a class 2 (double insulation) power supply (shall comply with > MIL-STD-461E) . I'm thinking on, what to do with the regular

EMC-PSTC needs some help.

personally rewarding experience. If you would rather talk with our on-the-line admins, feel free to contact either one directly: Michael Garretson:pstc_ad...@garretson.org David Heald: dave_he...@hotmail.com Best regards, Rich and Jim Rich Nute: ri...@sdd.hp.com

Re: TR: 60950 - Insulation between mains and secondary with capacitors

Hi Pierre: You did not state whether or not your secondary circuit is intended to be SELV or not. This is critical to your choice of capacitor. However, you did ask whether the circuit is equivalent to reinforced insulation, so I assume that your secondary circuit is SELV. By definitio

Re: Switch Inrush Ratings

Taking John Woodgate's usual response to such an inquiry, I did a Google search on "inrush." Surprisingly (to me), there is a wealth of reasonably good info on the web under the subject of "inrush," including switches rated for inrush current. Best regards, Rich ---

Re: SMPS Derating reqs for Altitude range of 5000-10000ft

Hi Chris, Andrew, Carmen: With regard to safety, both effects of altitude must be considered: 1) effect of air pressure on the electric strength of air (clearance), and 2) effect of lower density air on the temperature of solid insulation. (Creepage is a surface

Re: EMC-related safety issues

> No, it's simply that it isn't considered reasonable to have a radio and > a CFL in close proximity. If you want a lamp and a radio close together, > use an incandescent lamp. That's the bottom line, isn't it? Somebody has decided for me (in terms of what is "reasonable") that if I u

Re: EMC-related safety issues

Hi John: > >I've replaced the incandescent lamp on my bedside > >table with a new energy-saving compact flourescent > >lamp. With the lamp on, I cannot listen to even > >the strongest AM radio station on my clock radio > >(on the same bedside table) due to the lamp > >interf

Re: EMC-related safety issues

Hi Ken: > Trial lawyers and their clients have an obvious interest in portraying > consumers as helpless and child-like, and rich corporations as robber-barons > preying on the poor and weak. But why does the rest of society jump on that > bandwagon? Because profit and wealth, once

Re: EMC-related safety issues

Hi Ken: > The Forrestal incident occurred during the Vietnam conflict, July 1967. It > was pretty much as you describe except I would not say EMI was not > controlled. All DOD services had EMI requirements at his time. In fact, > 1967 was the year that MIL-STD-461 was adopted as a

Re: EMC-related safety issues

Hi George: > The key word in EMC is "compatibility". This implies that electrical and > electronic > equipment are (ideally) designed so that each can operate normally in the > presence > of another. This requires limiting both the emissions and sensitivity of > such > devices.

Re: Electric Shock and Water

Hi John: > >Is there a value (or range of values) for the > > resistance of water? > > The data exists; it depends, of course, on solute nature and > concentration. Try a web search. I did a web search before my post. There is lots of data on the use of water resistance an

Re: Electric Shock and Water

Hi Jason: Water comprises a 3-dimensional resistor. The value of the resistor depends on: * the "purity" of the water itself (the resistance is inversely proportional to the purity); * the dimensions of the electrodes (i.e., the conductors in contact with the wate

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 neutr

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 Euro

minimum distance for PWB inner layers (was creepage)

Hi Tom: > In 60950, applicable clauses are 2.10.5.3 and 2.10.5.1 (I'm not > reading genuine IEC/EN 60950, and I'm sorry if I'm wrong) - > the former states that distance through insulation would be applied > in such situation, and the latter set minimum thickness of 0.4mm > for supp

Re: Creepage on PCB Internal Layers

Hi Chris: > To me, it's sort of funny in that it just says that the Creepage and > Clearance distances do not apply on inner layers of void free PCBs. > That's nice; but I can't find where a distance is specified. I mean, I > would think that there should be some minimum distance betwee

Re: Creepage on PCB Internal Layers

Hi Chris: > To me, it's sort of funny in that it just says that the Creepage and > Clearance distances do not apply on inner layers of void free PCBs. > That's nice; but I can't find where a distance is specified. I mean, I > would think that there should be some minimum distance betwee

Re: Marking Languages for Canada

Hi Kris: > The markings on the power supply are: (also as per UL file) > Date code > model number > electrical ratings > "Class 2 transformer" > > The additional markings are: > "CAUTION", "Risk of electric shock" and "Dry location use only" and "Do not > expose to liquid,

Re: Marking Languages for Canada

Hi Kris: > A product from manufacturer X is delivered with a (direct plug-in) power > supply from mftr Y to customers in Canada. > Regarding the power supply, it is UL approved + UL listed and has the UL > marking with C and US. > The warning marking on the power supply is only in e

Re: Compliance Primer

It has been some time since I have had to explain or justify product safety activity to a high-level manager-type. As others have said, it is fraught with difficulties. Success depends on first determining the mindset of the person asking the question. I believe I would first ask a num

Re: medical-grade transformers

Hi Ged: > "In transformers with REINFORCED INSULATION or DOUBLE INSULATION the > insulation between 1ary and 2ary windings shalll consist of - > - 1 insulation layer having thickness at least 1mm, or > - at least 2 insulation layers with total thickness not less than 0.3mm, or >

Re: Bonding Impedance

Hi Ron: Two years ago, Jim Bacher presented my paper, "Equipotentiality and Grounding -- Deriviation of Grounding Resistance for Equipment" at the IEEE EMC Symposium Product Safety Workshop. This paper is available for download from the IEEE PSTC Mindcruiser web site: http

Admin message: posted advertisement

Today, a message was posted that violates IEEE emc-pstc rules against advertising. Here is our rule: - 5. Blatant or overt advertising of goods or services is not permitted. The listserver is provided as a service by the IEEE, whose policies prohibit anything that might be c

Product safety job at Hewlett-Packard San Diego

Hewlett-Packard Company San Diego site is looking for a high-level product safety engineer. The major job function is that of advising product designers on 1) innovative safeguards for new products, and 2) safety certification requirements for new products. The ideal candi

Re: TOUCH CURRENT LIMIT

Hi Xing Weibing: > We can read from table 5A of IEC60950:1999: > > Touch current limit for accessible parts and circuits not connected > > to protective earth: 0.25 mA > > question 1 : How does it (0.25mA) come from and what it is based on? For grounded (Class I) equipment for the home,

EMC-PSTC now functional

The EMC-PSTC listserver was down from Friday afternoon until today, Monday, late morning (Pacific Daylight Time). If you attempted to post a message during this time, the message was lost. Please re-send. We apologize for the inconvenience. If you have any questions or comments about this

Changing our safety standards (was 0.1 uF discharge)

Hi Gert: > I also tried the discharge between two fingers, and found the result to > be unpleasant at least. > Time to change standards... Now we must ask the question: Is the purpose of the standard to prevent injury or to prevent an unpleasant experience? I presume that

Changing our safety standards (was 0.1 uF discharge)

Hi Gert: > I also tried the discharge between two fingers, and found the result to > be unpleasant at least. > Time to change standards... Now we must ask the question: Is the purpose of the standard to prevent injury or to prevent an unpleasant experience? I presume tha

Re: Question: Discharge capacitance 0.1 uF

Hi Tom: > So, for voltage up to 450V d.c. (i.e. up to 318V a.c.), capacitor > up to 0.1uF will become a Limited Current Circuit, hence the voltage > is not Hazardous Voltage (1.2.8.4) - no additional condition would > be required for the capacitor connected to the primary circuit. El

Re: Question: Discharge capacitance 0.1 uF

Hi Tom: > So, for voltage up to 450V d.c. (i.e. up to 318V a.c.), capacitor > up to 0.1uF will become a Limited Current Circuit, hence the voltage > is not Hazardous Voltage (1.2.8.4) - no additional condition would > be required for the capacitor connected to the primary circuit. E

Re: safety testing in the USA

Hi Rob: > I am in discussions with a potential supplier of IT equipment, Its our > usual policy to request testing to a listed standard > such as UL 60950 for safety in North America. > > The supplier has replied that this is not mandatory. > > Is he correct? what compels safe

Re: safety testing in the USA

Hi Rob: > I am in discussions with a potential supplier of IT equipment, Its our > usual policy to request testing to a listed standard > such as UL 60950 for safety in North America. > > The supplier has replied that this is not mandatory. > > Is he correct? what compels saf

double-pole switching and fusing

Hi John: > I read in !emc-pstc that Crabb, John > wrote (incr.com>) about 'South Korean Power System', on Wed, 20 Feb 2002: > >Typically I would expect IT equipment to be safe if line and neutral > >were reversed, except for the issues relating to a single pole > >disconnect de

Re: Using PCB traces as transient voltage suppressor

Hi Chris: > 1. Can anyone else verify the breakdown voltage of 1Megavolt/meter for > air? Seems different than what I can remember; but I don't have a > reference handy. It also seems to me that this would be very dependent > upon humidity and pollution degree? In a separate messa

Re: Safety of Indicating LEDs

Hi Scott: > The scope of EN 60825-1 says LEDs are included whenever the word "laser" > is used, meaning they are to be evaluated the same way lasers are. Does > this apply to status indicating LEDs (non-lasing)? If so, are > manufacturers expected to test every status-indicating LED

Re: South Korean Power System

Hi Ed: With few exceptions, most power distribution systems have one pole of the supply, the neutral, grounded. (Indeed, the definition of "neutral" for single-phase systems is the grounded conductor.) In the IEC scheme of the world, a power distribution system where the neutral is groun

Japan mains frequency

> A good source is http://kropla.com/electric2.htm > . > > According to that site: > Japan100V50/60 Hz* > > *Eastern Japan 50 Hz (Tokyo, Kawasaki, Sapporo, Yokohoma, and Sendai) > *Western Japan 60 Hz (Osaka, Kyoto, Nagoya, Hi

Admin message -- format of posted messages should be plain text

A request from your list administrators... > Except... I (and other classic Compuserve users) won't see these messages > at all, unless and until they appear in someone else's REPLY in a form > Compuserve can send. It LOOKS great - but please don't send HTML to the > list. Cortland is

Re: OEM

Hi Richard: > We may soon be privately labeling our products for a particular customer, > and I have a question concerning the EU Declaration of Conformity. We will > be shipping products to our customer's distribution center, and they will be > responsible for sales to their customer

Re: My subscription may have terminated

Hi Dan: > I have received no emails today. Did my subscription cease? No, your emc-pstc subscription is not terminated. Today is the most unusual day in the history of emc-pstc in that there were no postings to the listserver between 5:30 PM PST Tuesday and 11 AM PST Wednesday. I, too

Re: Flammabilty requirement for cloth used on loudspeaker / UL6500

Hi Pierre: > Unfortunately, Hexamine is temporarely unavailable from IMSPLUS, and, > furthermore, this product cannot be sold outside the US. > > If somebody knows another source, he's welcome ! I did a Google search and found at least one more source: http://www.omahas.com/sto

Re: Flammabilty requirement for cloth used on loudspeaker / UL6500

Hi Pierre: > Reading the standard, I understand that the cloth used on the front of the > loudspeaker (external to fire enclosure) has to be tested according the > "tablet test" (see Table 13). As I recall (from the UL standard), the tablet is hexamine. I have purchased tablets from:

Re: Teslars???

Hi Joe: > We have a customer that is concerned about how our product, laboratory > equipment, will respond to electromagnetic disturbances from a high speed > train that runs close to their lab. The customer states that the > disturbance will be around 0.7-1.2 m Teslar. I believe yo

Re: TUV NRTL

Hi George: > However, for the U.S. OSHA establishes acceptable NRTLs, and the > CFR uses the words "NRTL", so I do not see how an electrical > inspector could object to what the Federal Government has sanctioned. The inspector must abide by the certifications approved by the local bui

Re: CE Marking - Prototypes

Hi Gregg: > My understanding if that: > > where OSHA is applicable then UL or equivalent is mandatory. True. However, replace "UL or equivalent" with "NRTL." > where OSHA is not application then Local Code is mandatory - and LOCAL > Code > requires NRTL (UL or equivalen

Re: Telecommunications Vs. ITE Product

Hi Gregg: > Let me start by asking one simple question - WHAT IS THE PURPOSE OF > CERTIFICATION? > > 1- to meet the legal requirement > 2- help market the product > 3- do the 'right thing' > 4- not to kill anyone > 5- make sure that the product is nor recalled > >

Re: Harmonic current emissions

Hi John: > >> But whichever method is adopted, the customer pays the bill eventually > and I > >> have more confidence in the highly competitive world of electronic > products > >> to come up with a cost-effective solution in a timely manner. > > > >One of the USA's major ob

Harmonic current emissions

Hi Keith and Ghery: There are a number of effects of harmonic current emission from non-linear loads. 1) When a large number of loads rich in triplen harmonics are supplied from a 3-phase source, the neutral current can be as high as root 3 of the phase current. (This effect d

Re: Company close down due to EMC phenomena

Hi Amund: I suggest you and your client and the regulatory authority meet to address the situation. Here are the issues as I understand them from your message: 1. In idle mode, the emissions are comfortably below the maximum allowed emissions. 2. In transmit mode, the emissions exc

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

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 --

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

Re: OFF is zero

Hi Stephen: > I think I missed the beginning of this thread, so > please forgive me if I rehash old ground. > > The 'vertical line' and 'circle' you refer to, are > actually a 1 ("One") and 0 ("Zero"); as in digital > logic on/off respectively. My original posting on this

Re: OFF is zero

Hi Serge: > O = Out of Circuit > I = In Circuit > > Note: while many people believe the symbols are O & 1, they are in fact > O & I IEC 60417 Symbols 5007 and 5008 are neither: the numbers 1 and 0, nor the letters I and O. They are the symbols depicted in the 60

Re: OFF is zero

Hi Neil: > The origin may be true, but IEC60417 is quite clear. ON is a vertical line > (symbol 5007) and OFF is a circle (symbol 5008). Agreed. And thank you for the clarification. Best regards, Rich --- This message is from the IEEE EMC

OFF is zero

A week or so ago, I asked about the origin of the 0 and 1 symbols for "off" and "on." I mentioned that it was my recollection that the the symbols came from early safety standards where the "off" and "on" functions were by means of a rotary switch where the 0/zero position was "off." I found

Origin of power symbols 0 and 1?

I am looking for the origin of the power symbols 0 (off) and 1 (on). The earliest standards that I have are CEE 10 and similar where the standard specifies something like: "Where a rotary switch is used for power, the 0 position shall be off and the 1 and higher position shall be o

Re: Creepage

Hi Richard: > What is a good source that explains the rational for the values for creepage > distances? There was a good deal of research done in the late '70s and early '80s on creepage distances and the deterioration due to deposition of foreign materials and the effects of humidity.

Re: Class III ID mark?

Hi Tom: With a bit further search, I found: http://w3.hike.te.chiba-u.ac.jp/iec417/html/doc/5180.html This site specifies the use and the referring standard: Application: On any kind of equipment. To identify equipment meeting the safety requirements specified for class

Re: Class III ID mark?

Hi Tom: > I guess what you think is IEC 60417 No. 5180, which shows "III" > in diamond shaped frame (45 degree rotated square). > (http://member.nifty.ne.jp/tsato/terms/iec417-5180.gif) Yes, this is the mark that was mentioned to me. > However, I don't know which standard require t

Class III ID mark?

A colleague recently showed me a Class III identification mark. However, he had no further information about the mark. (The Class III mark would be used to identify a Class III product similar to the way the Class II mark square-within-a-square is used to identify a double-insulated product.

Re: EN60950-1 Sect 2.5 Limited Power sources

Hi Tom: > Is it permitted to use PTC as an overcurrent protective device > for power sources not inherently limited? > I don't have EN60950-1 here, but I remember it must be a fuse > or other non-autoreset device. I said: "The trick is to determine if your test houses can

Re: Green/Yellow Earthing Leads

Hello from San Diego: One of our subscriber colleagues has pointed out that my assertion that Europe uses yellow as the color of the earthing wire is incorrect. I recall when the green-yellow was agreed to for power cords and internal equipment wiring. My recall was that both yellow and gr

Re: electric strength test

Hi Greg: > > >Why does "True SELV" require basic insulation > > >between SELV and earth? > > > > > >What is the hazardous voltage source, and what > > >is the current path through the body if that > > >basic insulation should fail? > > > > > > > > I believe (and I could

Re: EN60950-1 Sect 2.5 Limited Power sources

Hi Alex: > We use a linear (basically a transformer with a PTC thermistor) class II > SELV O/P stand alone power supply rated 10Vac, 5A. One of the labs tested > the O/P Isc with a direct application of the sc. The other lab tested the > O/P Isc by applying a load of 8A. The results w

Re: Green/Yellow Earthing Leads

Hi Peter: > What is the percentage of color over a surface area for the insulated > green/yellow earthing conductor. Is it better to have more yellow than green > or more green than yellow. I know North Americans prefer more green than > yellow and Europeans like more yellow than gree

Re: electric strength test

Hi John: > True SELV . requires double or reinforced insulation from hazardous > live parts/parts at hazardous voltages [different expressions used for > the same things] and basic insulation from earth. '950 SELV' allows SELV > circuits to be earthed (see 2.2.3.3 of IEC60950:1999

IT power distribution and Norway (was electric strength test)

Hi John: > >You may come across some distributors in Norway asking for DI or RI > >between PRI-EARTH, even for Class 1 power supplies. > > That's because Norway uses the 'IT' power distribution system, where > neither mains conductor is earthed directly, but one is earthed through

Re: electric strength test

Hi John: > That depends on which variety of SELV you mean. True SELV, as opposed to > '950 SELV', requires double or reinforced insulation from earth Why? Best regards, Rich --- This message is from the IEEE EMC Society Product Safety Technic

Re: electric strength test

Hi John: > >Y-caps have enough margin to easily withstand > >the 4300 V dc without damage. > > Without immediate failure, no doubt. But such a huge overstress may > cause latent damage that later results in failure, and, since IEC 60384 > doesn't call for such an over-voltage

Re: electric strength test

Hi Brian: > What I've always wondered about, at least for class 1 construction, is just > what is really being tested by the pri/sec hi-pot, when the customer chooses > to ground the power supply's return. (These comments presume the secondary is SELV.) When you use a ground for safe

Re: electric strength test

Hi Brian: > I am attempting to comply with both the letter and spirit of 60950:2000, cl > 5.2. Note that 5.2.2 allows for separate testing, according the type of > insulation required. When testing a (class 1) power supply, the withstand > level for primary to chassis is Basic; and f

Re: Criteria for UL V0 plastic enclosure

eet the HB flame class, hence my comment that he "may use any plastic." Best regards, Rich > Rich Nute wrote: > > > The choice is yours. If your product is supplied by a > > Limited Power Source, then you may use any plastic for the > > enclosure. If y

Re: Don'r Get Caught Running a Red Traffic Light!

Hi Doug: > I've only heard shortening the yellow light cycle > as an unconfirmed rumor. But I've been watching. > According to our local newspaper, the San Diego Union- Tribune, not only did the contract photo cops shorten the yellow light, they also moved the sensors. The contrac

Re: Flame Testing of Plastics

Hi Richard: > When testing plastics, the flame is applied for a specified period of time, > removed for specified period of time and the process is repeated for a > specified number of cycles. Is the procedure attempting to correlate with > observed fire patterns in equipment, or is i

Re: DC circuits

Hi Chris: > In other words: don't test if you know already the result before the test > is made. A good safety engineer can predict the result (not pass-fail but the measured value) of each and every safety test. For example, a good safety engineer can predict leakage current to wit

Re: Neutral/Earth connections

Hi Richard and Dave: In answer to Richard's comment: > The neutral is never to be tied to the chassis of equipment. It is not > allowed by any safety standard nor the National Electrical Code. The neutral > is to be tied to earth at one and only one point and that is that the > servi

Re: PCB temperature ratings

Hi Richard: > When a PCB is rated 105C or 130C or whatever, what does that really mean? > Can I really operate a 130C rated board at a maximum surface temperature of > 130C for years without being concerned about reliability or safety? Is there > a relationship between de-rating and r

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