[PSES] Tamper-proof Hardware

I notice that IEC 62368 mentions tamper-proof screws in a couple places (articles 0.8, 0.11), although not explicitly requiring them. It describes tamper-proof screws as providing a supplemental safeguard against hazards. I would take that to mean for level 3 hazards, for example mains terminal

Re: [PSES] Neat Funny Stories regarding EMI

Another CB radio story. If you remember, the big game was best distance. One operator out in Ohio had attached a linear, a roof antenna with rotor and was talking at quite a distance to someone down in the river valley. With the rotor he could simulate fading and such. He claimed he was mobile

Re: [PSES] IEC 62368-1 3ed, Final Draft International Standard (FDIS)

I object to the secrecy and closed aspects of the IEC standards process. A better example is the NFPA where revision cycles are rigorously scheduled, public input and change requests are welcome, proposals are openly debated and published, and the standard is publicly available. They still seem

Re: [PSES] Carbon Monoxide - Death Value

red CO limit. On Thu, Feb 16, 2017 at 2:29 PM, Robert Johnson <mailto:john...@itesafety.com>> wrote: In the US we sell about 15 million cars/yr and have about 300 deaths/yr from automotive carbon monoxide. Since DC power is available, the horn is available, pa

[PSES] Carbon Monoxide - Death Value

In the US we sell about 15 million cars/yr and have about 300 deaths/yr from automotive carbon monoxide. Since DC power is available, the horn is available, packaging is not needed, installation can be integrated in the auto manufacturing, I estimate an auto CO detector would cost below $10/car

Re: [PSES] Percentage Fill of Electrical Raceway in Machinery

For communications circuits (includes voice and data circuits /from a communications utility), NFPA 70 article 800.110 (B) applies which says:/ *800.110 Raceways and Cable Routing Assemblies for Communications Wires and Cables.** **(B) Raceway Fill for Communications Wires and Cables.* "The race

Re: [PSES] 208 split-phase?

Essentially all residential electrical services in the US are 120/240 volt split phase services. Electricians call this single phase service. As an electrical engineer, I like to think of it as two phase service, with phases at 180 degrees. You will not find residential service provided 208 v

[PSES] Fwd: Re: [PSES] NEC

Forwarded Message Subject:Re: [PSES] NEC Date: Thu, 24 Jul 2014 15:52:16 -0400 From: Robert Johnson To: Boštjan Glavič The code provides requirements for wire gauge (AWG). The gauge needed for a specific ampacity depends on many variables like ambient

When UL component recognition is not enough.

I have a complaint about a certification process where agencies are providing approvals of little value. There are products for sale which have been reviewed (for example) to UL 1950, and are currently being manufactured and UL recognized. UL 1950 is a withdrawn standard, replaced by UL 60950.

Re: FW: European Equivalent for: National Fire Code, National Electric Code, Uniform Building Code, and OSHA

Since they've only been at harmonization a short while, it will probably be some time before we see much commonality in a code area with well established traditions. >From NFPA: European Committee for Standardization (CEN) CEN Technical Committee 250: Stru

Re: FW: European Equivalent for: National Fire Code, National Electric Code, Uniform Building Code, and OSHA

NFPA has been trying to fill the common international standard roll in the electrical and fire codes business http //www.nfpa.org/categoryList.asp?categoryID=215&URL=International. It has had pretty good luck with third world countries and the far east but has had limited success in Europe, partly

Re: Ethics grad work Therac-25

Thought it would be interesting to review what we have recommended a grad student acquire. I hope he has a good library. I brings up the problem of trying to make the right moral decisions. I assume anyone writing safety related software will start with this. CHF $ IEC 61508-SER 1216 1,168

Re: 5 mA earth-leakage trips in USA

I think you will find the typical GFCI trips about 7 mA. GFCIs have been responsible for a significant reduction (30%?) in electrocutions and their required use has expanded in the code to include outdoor locations and almost every damp environment like baths, kitchens, bars, basements, pools, mari

IEC 60950 Clause 6 questions

I have a couple questions about the use of Clause 6 of IEC 60950. First: In order to pass the “Pass 6.1.2” block, the test of 6.1.2 is applied. A voltage of 120 volts is used for figure 6A. If a grounded circuit is used, and the exclusions of 6.1.2.2 apply, then the test of 6.1.2.1 is not use

Blocked ventillation testing

I have been requested by UL-HongKong to the blocked ventillation abnormal testing with all vents on all side blocked simultaneously. My previous experience has been that one side is blocked at a time. Blocking more than one side at a time was considered multiple faults. If it passes blocking

RE: 94V-0 question

This is a multi-part message in MIME format. I might add that almost any plastic or fiber will pass 94V-0 in application if adhered to the metal enclosure. The heat sinking makes it almost impossible to burn. Bob Johnson ITE Safety From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...

RE: 3-Phase Power Question

Others have correctly identified the typical configuration. This can also be generated by an open delta (two transformers). This is sometimes used to provide three phase service to a small business customer with only one or two three phase loads. You start with the customary 120/240 single phase c

RE: Wire Colors

This is a multi-part message in MIME format. I would recommend you provide a letter from the manufacturer (you?) instructing approximately as below. Conductor re-identification with tape is permitted by the code and better explained in the code handbook (ref 310.12). Keep in mind a disconnect devic

RE: Surge Suppressors on a UPS

This is a multi-part message in MIME format. So much for extension cords. I assume the UPS manufacturer claims his product is unsuitable for use with all computer products containing surge suppressors. Bob Johnson ITE Safety Title: RE: Surge Suppressors on a UPS So much for extension cor

RE: AC shut-down

This is a multi-part message in MIME format. I have seen no reports of such code activity. Shutdown for smoke or operator choice is required in computer rooms, but not required as part of a general building alarm. Any building shutdown of ventilation would have to be coordinated in some cases since

RE: AC outlet max current

same. I've come across no duty cycle limitations for this situation. Bob Johnson ITE Safety From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of JP Hare Sent: Tuesday, May 06, 2003 11:05 PM To: Robert Johnson; emc-p...@majordomo.ieee.org Subject: RE:

RE: AC outlet max current

uit cables and conduit to conditions which will not degrade insulation. Bob Johnson ITE Safety From: Tyra, John [mailto:john_t...@bose.com] Sent: Wednesday, May 07, 2003 9:13 AM To: 'Robert Johnson'; 'JP Hare'; emc-p...@majordomo.ieee.org Subject: RE: AC outlet max current

RE: AC outlet max current

A noncontinuous load is permitted to use 100% of the circuit rating. Only continuous loads need the derating. Bob Johnson ITE Safety From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of JP Hare Sent: Thursday, May 01, 2003 12:20 PM To: Gonzalez, Kenn

RE: AC outlet max current

This is a multi-part message in MIME format. NFPA 70 Clause 210.19(A)(1) ITE equipment is considered a continuous load. Bob Johnson ITE Safety From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Gonzalez, Kenneth P (Rocky) Sent: Wednesday, April 30,

RE: Surface Temperature Limits

The changes have forced many who simply matched test rises to rises in the standard and assumed they were OK to do the testing right. It is now much more obvious that you need to account for recommended product ambient. If you have a 25 degree max product ambient, say so. Strictly speaking, a cha

RE: high immunity

This is a multi-part message in MIME format. I assume this will wipe out all humans with pacemakers either by direct electrocution or by destruction of their pacemaker. Bob Johnson ITE Safety From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of drcuth

RE: Fire Retardants

We experienced this problem with a small computer fan about 30 year ago. The fan bearing would fail after a few years, the fan would stall and impedance protection allowed the fan to sit and cook for months. Eventually the insulation failed and allowed an arc. The plastic at this point had lost it

RE: Term in Electricity

It's hard to tell the limits of your inquiry. In simple US NEC terms, there is no special name for the termination of the "grounded conductor" or neutral at the load. However, you can have star connected three phase loads and view the neutral as a star connection point. It simply is not a code def

RE: Ethernet coax connection

This is a multi-part message in MIME format. If you have shock level differences between the grounds in two different buildings, either an entire building isn't connected to an earth electrode, or someone is paying a whopping electric bill to heat up mother earth. I suspect the shock situation you

RE: Fuse Holders

This is a multi-part message in MIME format. You may want to consider using the fuses outside their rating. If you can show the fuse is not needed for safety purposes by bypassing the fuse during safety tests, and show that if the fuse does operate, no hazard results (this may be an issue with high

RE: best screw/washer choices for attaching PCB to Chassis?

m not so concerned about arcing here. However, it would be interesting to understand this better for future designs. In fact I might be more concerned about the screw actually coming loose as a result of this compression, however I've never heard of such a thing. I guess that returns me to m

RE: Class 2 circuit requirements - UL1310

This is a multi-part message in MIME format. The class 2 requirements used to be specified by the National Electrical Code. The situation is slightly different now in that Class 2 circuits are now defined in the Listing requirements, e.g. UL 1310, UL 60950, etc, with direction to the standards comm

RE: best screw/washer choices for attaching PCB to Chassis?

This is a multi-part message in MIME format. You should not include the PWB as part of the sandwich in an electrical connection. It gradually squashes and leaves a loose connection. The answer is generally to use a soldered jumper and lug to make connections from board to chassis. The same applies

RE: Ethernet Creepage and Clearance

This is a multi-part message in MIME format. IEC 62102 (Table B.1) declares that for safety purposes Ethernet 10base5 is considered a TNV-1 circuit. Other Ethernet circuits are considered SELV. The internal circuits they connect to in your case are likely to be SELV (although not necessarily, for e

RE: Maintaining conductivity of freshly machined aluminum

There is a product by Ideal called Noalox specifically for the application of preventing deterioration of aluminum connections, primarily for the electrical trades. It is an anti-oxidant joint compound for use on connectors and aluminum wire, a grey paste which does not appear to dry out. It is ap

RE: Circuit Breaker Tripping Dring Fault Tests

  Two points: To assure the safety of your product consider not whether it is safe if the breaker trips, but what is the failure mode of your product if the breaker (which you do not provide) does not trip. If you rely on the breaker, you need to properly specify it. In the US, there have been c

RE: CE for IP Phone

Which brings us to the odd conclusion that the only people who really care what approvals apply are the customs officials. We should probably be asking them what they expect since they appear pretty autonomous. Bob Johnson ITE Safety -Original Message- From: Peter L. Tarver One point

RE: Undervoltage/Overvoltage Effect on Household Appliances

Peter, You'll probably get no more than anecdotal feedback, so here's mine. Regarding undervoltages, I can think of nothing damaged by low voltage in itself, only its consequences. The primary cause is the need for some products to maintain its power output or speed. For a lowered voltage, you ge

RE: ITE standard - hot air

Vijay, I am not aware of standards specifying this, but in practical terms, heat transfer would depend on airspeed, time, surface area, etc. For example, high speed air would burn much faster than convected air. If this is a significant safety concern rather than a standards compliance question,

RE: docopocoss

Bob Johnson ITE <http://www.itesafety.com/> Safety -Original Message- From: Robert Johnson [mailto:john...@itesafety.com] Sent: Tuesday, November 05, 2002 5:34 PM To: 'Rich Nute' Subject: RE: docopocoss "docopocoss" This word was un

RE: Mobile Power Cart

Peter, You are right, the standard does address movable equipment, but movable equipment is not even mentioned with regard to the stability tests of 4.1. It only uses the term relative to fire enclosure and leakage current. The stability tests are essentially unchanged since the larger computer

RE: NEBS, Raised Floor Substructure Standards

Several raised floor issues in addition to earthquake need consideration before RBOCs make a transition. - Does this mean a transition from front to back airflow to vertical airflow? Is the underfloor area the supply or return plenum? Vertical cooling is more susceptible to heating from adjacent p

RE: Mobile Power Cart

Note that 60950 stability requirements are intended to address equipment which is not in motion. It is inadequate to address moving carts. UL 1667 and UL 1678 are meant for that purpose. The first was in response to the deaths of children moving televisions in schools. Moving carts are prone to t

RE: Ground potential differences

Most earth potential differences come from load currents. Leakage currents don't usually add up to very much. Electrical installations should have one neutral to earth connection at the source of the system (at the transformer or service entry). However many electrical installations have branch pan

RE: New EU regulations - civil aviation

One thing that surprises me about avionics is the reports of spurious and misleading readings from instruments due to interference. It seems in these days of error checking and verification that we should be able to make instruments which are either confident of the data received or capable of repo

RE: EN60950-1 Sect 2.5 Limited Power sources

1. What is the correct method to test for a Limited Power source in determining what enclosure is required? The Isc limits must be met regardless of the load, not only at 30a or 8a. You need to do sufficient testing to satisfy yourself it will comply in general.

RE: Curious about Tripp-Lite "isolation transformer"

The transformer generates what the code call a "separately derived system." Typically such circuits are grounded (earthed). For US requirements see the National Electrical Code articles 250.21 and 250.22. The isolation transformer reduces common mode (supply vs ground) noise. That is its primary pu

RE: requirements for ITE power cords

Sorry to knock your "substantially built" comment, but the derating is not based on the plug. In fact the 15 and 20 amp plugs are the same construction with different configuration. Both can be used at full rating. The circuit they are used in contains the limitation. The derating on North American

RE: Nema 5-15R sockets

In fact, soft copy of NEMA WD-6 from www.nema.org is free!! If only IEC ... Bob Johnson ITE Safety -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of ron_well...@agilent.com Sent: Monday, July 22, 2002 9:02 AM To: jim.eich.

RE: IEC60320

IEC 60320 is a standard for the appliance coupler (male and female, cord and chassis styles) in assorted configurations (to cover assorted ampacities, temperatures, 2 or 3 wire) and does not include fuseholder specs. See UL 512 or CSA 39 for fuseholders, I don't believe there is an IEC fuseholder s

Re: Nema 5-15R sockets

The NEC does not establish an orientation. Proposals to establish an orientation have been proposed to the code panel and rejected. See http://electrical-contractor.net/ubb/Forum2/HTML/000553.html for a discussion. You will find ground up preferred by some to provide protection as mentioned by

Surge protection

In light of recent discussions about overvoltage protection, the following document announcement from IEC should be of interest. IEC/TR 62066 (2002-06) Ed. 1.0 Surge overvoltages and surge protecti

RE: TOUCH CURRENT LIMIT

The history is lost in committee activities from years ago, but I can provide my own thoughts. The limit for accessible parts on circuits not connected to protective earth is set below the threshold of sensation, since that current is likely to pass through the user in normal use if he touches the

RE: NEC Questions

1) Correct, this cannot be used in a multiwire branch circuit since it may eventually be removed without being bypassed. The concern is that an open neutral in a multiwire (e.g. 120/240 3w or 120/208 4w) circuit leaves loads connected in series phase to phase. The voltage across a product intended

RE: Physical Protection of Flexible Power Cords

You're already on the edge of the code with this one. You describe the equipment as permanently installed. Under those circumstances you normally could not use flexible cords. You might use the condition "400.7 (6) Connection of utilization equipment to facilitate frequent interchange" to permit th

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

Peter, For your equipment special consideration of transient levels is needed. Refer to annex G of 60950. If you power the pole mounted equipment from overhead lines as do streetlights, you are likely to be overvoltage category IV which might mean mains transient levels of 4 or 6 KV. If the camer

RE: Safety: Temperature Rise and Capacitor Clearance (EN 60950)

In response: > I have a couple of questions regarding this standard: > (I have the 1992 version) It's time to upgrade to current versions. Check: http://www.iec.ch/cgi-bin/procgi.pl/www/iecwww.p?wwwlang=E&wwwprog=cat-d et.p&wartnum=027973 for the latest version still in the process o

RE: EN 61000-3-3 compliant heater controller

I don't have much to say about flicker, but maybe I can reduce your skepticism about harmonics. I have had three experiences regarding failures caused by third harmonic currents. The first was with mercury vapor lighting fixtures. An array of 1000w 277v single phase ballasts in hibay lighting f

RE: EMC-related safety issues

The latest IEC "Just Published" points to an article on this subject http://www.iec.ch/etech/etech-live/frames-prod-e.htm It discusses the application of IEC 61000-1-2. Also of related significance when talking about safety of complex systems and the impact of outside influences like EMC is IEC 6

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

While the question and discussion related to SMPS, and brought up spacing and cooling issues, you might also consider the rest of the system. Disk drives in the past have had altitude problems due to flying height of heads. I assume this is still an issue since technology is always pushing the l

RE: 2 Phases in North America

This has just reopened the old two phase controversy again. Ed has done a good job of describing the systems in detail, but be careful with the terms. Ask an electrical engineer about a 120/240 volt home service and he will call it a two phase system. Two phases 180 degrees out of phase is technica

Sometimes product safety just isn't enough

I couldn't help passing on this reference to a bit of unforeseeable misuse. http://electrical-contractor.net/ubb/Forum4/HTML/48.html Bob Johnson

Re: Class III anomoly

This came up at IEC TC74 WG8 and was the object of several proposals. We could come to no agreement about whether Class III included TNV, earth connections, internally generated voltages of assorted energies, etc., so we dropped the subject. It plays no part in the safety requirements of IEC 6

Re: Class III anomoly

This came up at IEC TC74 WG8 and was the object of several proposals. We could come to no agreement about whether Class III included TNV, earth connections, internally generated voltages of assorted energies, etc., so we dropped the subject. It plays no part in the safety requirements of IEC 6

Re: How Safe ???

While the US legal system is subject to a lot of frivolous lawsuits, product liablilty is often the only thing keeping companies on the straight and narrow. We have already seen lots of correspondence in this newsgroup about justifying agency approvals, the use of safety standards, or other c

Re: Oils for the 950 Hot Flaming Oil Test

If you are looking for a specification for the oil, the MSDS is not necessarily the appropriate place to look. The MSDS is for the purpose of defining toxicity and similar risks and is often the same for a range of materials. As we were writing the standards we found it difficult to come up w

Solstice electrical shutdown

I've been wondering about the safety consequences of the suggested load shedding expected tonight. A chain letter which has gained a lot of popularity recommends turning off all electrical use from 7 to 10pm in celebration of the solstice and in reaction to the recent west coast power problems

Re: Lasing LEDs

I would expect a simple correlation is difficult or has a reasonable margin. I have been told in the past that for some products, they have been tested and sorted following production for high output without laseing. I suggest you work with the LED manufacturer's recommendation. Since the nam

Re: SELV vs ELV

ELV has only one level of protection between hazardous voltages and the user. SELV requires two. See UL 60950 for further explanation. Hard to tell what the connector has to do with it. Ask for the conditions of acceptability from the power supply report. You may be able to salvage the sup

Re: 950 Pollution degree detirmination

The following is from IEC TC74's document 74/585/NP on Equipment Installed Outdoors, a proposed supplement to IEC 60950. It has not been adopted, but give an idea of the current thinking in TC74. IPX6 is not addressed, but reference is made back to IEC 60950 for Pollution degree 1. It looks li

Re: Harmonics -- WSJ opinion.

Years ago Digital Equipment Corporation had problems with power distribution in office module systems. As I recall, it was a combination of phase balancing of loads and harmonic currents in the neutral. A module system which distributed three phase 5 wire power and indicated the phase connectio

RE: Unreliability of earthing/groiunding

An excellent elaboration. Norway is not the only place with rocks. Rock really has little to do with the issue. A common equipotential environment is the goal. It's unfortunate we ever started with the terms earthing or grounding. In the US, the code requires this environment be created by comm

Re: Seeking assistance from Chemical Experts

As I recall, the requirements for label durability came years ago from UL, where the original test specified kerosene. As the standards evolved, propagated and became international, the term kerosene was complained about since it varied worldwide. In attempts to be more specific, someone came

Re: Sharp edge & point

gt; Raymond Li > > -Original Message- > From: Robert Johnson [mailto:robe...@ma.ultranet.com] > Sent: Tuesday, 17 October, 2000 06:23a > Cc: emc-p...@majordomo.ieee.org > Subject:Re: Sharp edge & point > > It's also available directly from UL. It i

Re: Sharp edge & point

It's also available directly from UL. It is not very sensitive. It takes a very sharp edge to fail. It is not for testing points, only edges. I find it mainly of use to settle arguments. It also seems it would be rather variable if it came from several different manufacturers. After some experienc

Re: Label Rub test per IEC60950

As I recall, the chemical that was described is what is sold in the US as kerosene. It appeared way back in the early UL standards that way. Since this is a petroleum distillate characterized mainly by its molecular weight and what temperature it comes off the refining process, describing it is ki

Re: Wiring under raised floors

Cables under raised floors are currently the subject of a proposal to change the code regarding them as follows: 12-101 -( 645-5(d)(5)): SUBMITTER: Rick Zupan, Lake Oswego, OR RECOMMENDATION: Revise as follows: 645-5(d)(5) Cable, other than those covered in (b) and (2) and those complying with (a)

Re: Implanted IC in brain

It's just another new product. We'll have to work out the bugs. After all, we already have ICs implanted in our hearts, or at least nearby (pacemakers and defibrillators), and in our ears (cochlear implants). It'll be useful to have a calculator at the ready. I wonder if we'll choose algebraic o

Re: Connecting to the cable TV system.

The National Electrical Code NFPA 70 Article 820 (and maybe 830) would apply. Bob Mike Morrow wrote: > Besides 15.115 and 15.118 of FCC Part 15 can anyone point me to other > standards / requirements for connecting to the cable system? If I meet > these two sections can I connect any device to

Re: Acoustic tests UL1950 clause 6.4.3 for ISDN modem

UL has stated that the burden of acoustic limiting can be placed either on the headset or the host equipment. This was discussed at the UL's IAC meeting in January. You can contact Tom Burke for information from the minutes. They would probably expect you to explain to the user that the headset ne

Re: Prefered Fuse Values

Just because you have a filter rated 6A, it does not mean you need to protect it with a 6A or smaller fuse. With regard to ITE standards, if your product passes safety tests without a fuse, relying only on branch circuit protection, you are not required to have a fuse in the product. If your pro

Re: TNV-2 to SELV Spacing

The insulation type needed and conditions of use are described in IEC 60950 table 2G, probably basic (exceptions in 2.3.2) For clearances, unless you know the voltages to be otherwise (e.g. proprietary circuits), TNV2 (add in your SELV voltages) has a voltage up to 200Vp to earth (M.3.1.2) and a

Re: High voltage testing and altitude correction factor

If you trace down the location of the breakdown, I'll bet you'll find spacing violations there. There is a pretty good margin built into the dielectric strength tests. I often go well beyond the test limits on type tests just to find the weak spots and assure a margin for production tests. (Comp

Product safety effect on child mortality

A recent article in Business Week indicated a decline in accidents and injuries was a substantial reason child mortality has fallen between 1960 and 1990 (by 57% for 1-4 year olds and 48% for 5-14). A report by economist Sherry Glied of Columbia University cited by the article http://ideas.uqam.c

Re: UL544 Leakage Limits Patient Equipment*

It may not be important whether you call it an applied part or not. You are not making a direct electrical connection to the patient. In any case you should meet the leakage requirement. This should be easy with properly insulated earphones. IEC 60950 also addresses this issue and throws in more c

Re: EMC and product safety split?

If the group is split, common and peripheral topics would have to be sent to both groups. Those interested in one topic would have less to sort through, but those interested in both would have to filter duplicates. I see no total gain but added administrative burdens. Don't ask for subject codes.

Re: Design Guidelines

I'll not try to write it for you, but parameters you need include for wire: - dielectric strength (associated with insulation thickness) - ampacity - durability - flammability - temperature - color - agency approvals (and associated markings) for connectors: - creepage, clearance and thickness di

Y3K

Y3K.doc Description: MS-Word document

Re: UL in Washington Post - Seagull

I'm afraid I don't understand many of the points in the article. It is a bit like what we call a seagull (it flies in, dumps a load of shit and flies away, leaving someone else to deal with the mess). "National Association of State Fire Marshals is considering challenging UL's tax-exempt status be

Re: 60 Hz Power Line Impedance

d to have a problem. Voc is easy, but Isc is more of a > breaker response test. Someone must have an interesting procedure for > powerline impedance testing, maybe defining some time limit. > > Ed > > > -----Original Message- > > From: Robert Johnson [SMTP:robe...@

Re: 60 Hz Power Line Impedance

Can't you just measure the open circuit voltage and the short circuit current? "Price, Ed" wrote: > As to measuring the AC power source impedance, well, time to go home now! > > Regards, > Ed - This message is coming from the emc-pstc discussion list. To cancel your subscription, send

US Metrication, RE: Update on UK conduit entry dimensions

Changing the thread of this topic a little, the US NFPA (National Fire Protection Association) has a proposal for change regarding metrication of the National Electrical Code (NEC). This is sponsored by the NEC Technical Correlating Committee, at the direction of the NFPA Standards Council, so I wo

Re: Attachment Plugs and Power Cords

If you went to the store to buy a TV and one of the sets came without a plug on the end of the cord, what would your thoughts be? You can get away without plugs in some markets, but most customers expect a functioning product, not a do it yourself project. "WOODS, RICHARD" wrote: > I can find no

Re: Flamible Liquids and Vapors

Refer to IEC 60950, 3rd edition, clauses 4.3.12. and 4.3.10. Bob Johnson Brian At Work wrote: > Hello Group, Our company is working on a small laboratory device, > about the size of a computer tower, that contains, in addition to > electronic components, about 1 gallon (3.8 liter) of a solvent

Re: Lightning and GFCI

> Yes, lightning can damage GFCIs I had one destroyed in my house. It punched a > hole from a phase electrode right into the side of the solenoid and out the > other to ground. Not much that lightning can't take out. > > The test you suggested is just that done by the test button. It connects a > r

Re: US NEC and Canadian CEC

If it were that simple, so would be the codes. You asked a lot of questions without reducing the scope. Answers depend on the application. For example ampacity depends on temperature which in turn depends on environment (ambient, buried, aerial, in conduit, in concrete, or other dissipation factor

Re: Brown-out..

It's more typical to provide an operating voltage range for your product, and let the customer decide if he is happy with what he expects for brown-out voltage. >From a manufacturer's standpoint, it is good to find out what the actual operating characteristics of your product are, for example wha

Re: SELV/TNV-1, TNV-2, TNV-3/ HAZ/SEC Ratings for Various Interfaces

This process is already underway by IEC TC74. Refer to docujment 74/502/CD, "Draft Technical Report, Electrical Safety; Classification of interfaces for equipment to be connected to information and communications technology networks." (about 30 pages) Available from your country's IEC TC74 technica

Re: IEC60950 3rd Edition

IEC does not withdraw a standard. It has no need since it does not impose the standard. It eventually becomes unavailable for purchase. Countries or certification agencies which have implemented the standard into law however create withdrawal or expiration dates. You will see these dates as the n

Re: White neutrals in Europe

Not well addressed. You could - request a formal interpretation from NFPA asking if light blue leads would be sustantially equivlaent to white or gray as described in 400-22c, or - request a code change to appear elsewhere in the code. Bob miksher...@aol.com wrote: > The referenced NFPA 70 secti

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