Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
In message <63056535adcf774b87d41a999d9a7f2b23732...@bct1e2k301.americas.tsp.ad>, dated Tue, 21 Dec 2010, "Goedderz, Jim" writes: >Is there any additional response to Pat's inquiry? I would also like to >know the justification of a VDR/gas discharge tube connection in the >primary circuit. > >It would be useful to have that available. Some information became available very recently. This is not a standard or even an official interpretation of a standard. I suppose it is advice having a strong provenance: TC108 position on varistors having connection to the mains, also identified as voltage dependent resistors (VDR) and metal oxide varistors (MOV). During the recent TC108 meetings in Seattle, October 2010, the use of varistors having connection to mains circuits was discussed. There seemed to be different opinions and interpretations regarding the requirements contained in several of the TC108 standards. This INF document is intended to clarify the current interpretation of TC108 on those aspects where agreement has been reached. Some issues are still under discussion and these will be explained as soon as possible. Existing requirements not addressed below remain applicable. The following statements are supported by the experts and the management of TC108 on the application of varistors in the IEC 60065, IEC 60950-1 and IEC 62368-1 standards. -- Compliance with IEC 61051-2 Where a varistor is used in connection with the mains, it shall comply with IEC 61051-2. The combination pulse test of IEC 61051-2:1991, Am 1:2009 (2.3.6, Table I group 1 and Annex A), including consideration of the nominal mains voltage and overvoltage category, should be allowed as an alternative to the requirements in the current standards. Protection of varistors Where a varistor is used in parallel with the mains connection, it should be protected against temporary overvoltages, overloads or short circuits. Details can be found in IEC 60950-1, clause 1.5.9.2. Varistors in series with a GDT (for all types of equipment, including 'normal' Pluggable Type A equipment) Where a varistor in series with a GDT is used to bridge BASIC INSULATION, the following applies: – the varistor has to comply with IEC 61051-2 as indicated in the standards; and – the GDT has to comply with: • the electric strength test for BASIC INSULATION; and • the external CLEARANCE and CREEPAGE DISTANCE requirements for BASIC INSULATION. It should be noted that the use of a VDR in series with a GDT to bridge reinforced insulation was also discussed. So far, no agreement was reached within IEC TC108. -- It should be noted that each of the mentioned standards is currently being revised under the TC 108 maintenance procedures and these clarifications will be introduced in the relevant standards as deemed necessary. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK Plural: data, criteria. Singular: datum (different meaning: use 'data element' for a single item), criterion. 'Effect' is a noun, 'affect' is a verb (except in psychiatry). - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Is there any additional response to Pat's inquiry? I would also like to know the justification of a VDR/gas discharge tube connection in the primary circuit. It would be useful to have that available. James Goedderz Sr. Principal Engineer-Product Safety Sensormatic Electronics, LLC 561.912.6378 -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of pat.law...@slpower.com Sent: Wednesday, December 15, 2010 9:05 PM To: emc-p...@ieee.org Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. I found this in UL 60950, clause 1.5.9.1: -- quote --- If a surge suppressor is used in a PRIMARY CIRCUIT, it shall be a VDR and it shall comply with Annex Q. NOTE 1 A VDR is sometimes referred to as a varistor or a metal oxide varistor (MOV). Devices such as gas discharge tubes, carbon blocks and semiconductor devices with non-linear voltage/current characteristics are not considered as VDRs in this standard. --- end quote --- This sounds like it prevents the use of VDR/gas discharge tube combinations to limit primary-to-earth line surges, or gas discharge tubes in the primary completely. Is this correct? I'll bet the gas tube companies are having heartburn over this. Pat Lawler EMC Engineer SL Power Electronics Corp. ri...@ieee.org wrote on 12/15/2010 12:05:18 PM: > On 12/15/2010 11:41, Kunde, Brian wrote: > > Does it make VDRs safer to use them in series with a gas-tube like some > > do with Varistors? > Hi Brian: > > Yes. > Today, this is the trend among manufacturers that > want to use a VDR between mains and earth. > And, TC108 is still trying to sort out the requirements > for both devices in such a circuit. > > Best wishes for a Merry Christmas, > 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 > All emc-pstc postings are archived and searchable on the web at: > http://product-compliance.oc.ieee.org/ > Graphics (in well-used formats), large files, etc. can be posted to that URL. > Website: http://www.ieee-pses.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 > Mike Cantwell > For policy questions, send mail to: > Jim Bacher: > David Heald: - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
As I previously mentioned, the hi-pot test is for SOLID insulation. Presumably, the insulation between the side panels and the mains circuits is air, or air in series with solid insulation. So, it should be valid to test without the side panels. Merry Christmas! Rich On 12/16/2010 06:16, Kunde, Brian wrote: > Here is another clunky suggestion. What if you put your Surge Suppressor > circuit after a dual pole circuit breaker that is only energized when > the device is powered up. That way, the VDR is out of the circuit during > the Hipot test, but in-circuit during the Surge Immunity test. > > This brings up a good point in regards to production hipot testing. Some > of our instruments have double pole relays, so during hipot those > downstream circuits do not get tested. So those circuits have to be > individually hipot tested before the side panels are installed. As you > said, this goes against the intent of the production hipot test, but > what else can you do? You do the best you can. If an inspector > disagrees, have him give you the solution. > > The Other Brian > - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
A solution we used years ago involved three elements in series, the VDR, a gas tube and a fuse. The gas tube prevented the development of leakage currents as transients age the VDR. If the VDR failed, the fuse prevented full line to neutral fault currents through the gas tube in the event of transients. Removing the fuse also allowed disconnection of the circuit for hipot testing. This was used as a fix for an existing design, but for cost reasons was avoided in new products by better product design. Bob Johnson On 12/15/2010 05:18 PM, JIM WIESE wrote: > Thanks Rich, > > Your first paragraph is what I tried with the safety lab to no avail as > they still required a factory hipot, which requires disassembly or some > other form of clunky workaround as Brian mentioned. Brian's method > could be feasible in some cases from the safety perspective to remove > the MOV for the hipot, but lousy if you need a low impedance reliable > path for thousands of amps of lightning current. It also is not > feasible in most cases for potted or OSP sealed telecom equipment. > > Merry Christmas, > > Jim > > Jim Wiese > Senior Compliance Engineer > ADTRAN, Inc. > 901 Explorer Blvd. > Huntsville, AL 35806 > 256-963-8431 > 256-714-5882 (cell) > 256-963-6218 (fax) > jim.wi...@adtran.com > > > -Original Message- > From: Richard Nute [mailto:rn...@san.rr.com] > Sent: Wednesday, December 15, 2010 4:06 PM > To: JIM WIESE > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and > VDR bridging basic insulation. > > > > Hi Jim: > > > If the equipment is permanently grounded, then > you can put in a VDR/MOV between mains and ground. > Think of a permanent ground as a reinforced > safeguard, with no need for basic insulation (in > my opinion). > > For cord-connected equipment, IEC 62368-1 will > likely require a series circuit of VDR and gas > discharge tube. > > The big problem with VDR/MOVs is that we don't > know the energy that must be dissipated by the > VDR/MOV. If the energy is high enough, the > VDR/MOV will be destroyed and you will have arcs > to ground. > > > Have a Merry Christmas! > Rich > > > > > On 12/15/2010 13:06, JIM WIESE wrote: > >> Hey Rich, >> >> The reason for VDR's (MOV's) to ground is to prevent arcing to the >> chassis for customers that demand either 6KV or 10KV lightning tests. >> The products are permanently grounded so the arcing to ground is not a >> safety hazard at those levels. The products easily pass the hipot >> without the MOV's to several KV (well above the hipot level). >> >> The arcing at 6 or 10KV often functionally kills the supply or other >> circuitry, which of course 60950 could not care less about >> functionality. But other standards do. >> >> It sounds like IEC 62368 will mess up using MOV's to ground though as >> > I > >> am not aware of MOV's rated several KV. >> >> Best regards, >> >> Jim >> >> Jim Wiese >> Senior Compliance Engineer >> ADTRAN, Inc. >> 901 Explorer Blvd. >> Huntsville, AL 35806 >> 256-963-8431 >> 256-714-5882 (cell) >> 256-963-6218 (fax) >> jim.wi...@adtran.com >> >> >> -Original Message- >> From: Richard Nute [mailto:rn...@san.rr.com] >> Sent: Wednesday, December 15, 2010 2:01 PM >> To: JIM WIESE >> Cc: EMC-PSTC@LISTSERV.IEEE.ORG >> Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and >> VDR bridging basic insulation. >> >> >> >> Hi Jim: >> >> >> Thanks for your remarks. >> >> You CAN remove the VDR during hi-pot testing. >> This is specified in 5.2.2: >> >>"To avoid damage to components or insulation >>that are not involved in the test, >>disconnection of integrated circuits or the >>like and the use of equipotential bonding are >>permitted." >> >> This is for the "type" test, not the "routine" >> test. Nevertheless, your point is well taken. >> >> Also note that 5.2.1 specifies: >> >>"The electric strength of the SOLID INSULATION >>used in the equipment shall be adequate." >> >> So, the hi-pot test only applies to solid >> insulation. >> >> The other option is to specify the VDR at a higher >> voltage than the hi-pot test voltage. >> >> Regarding VDRs, I don't know why any equipment >> would need a VDR between m
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
I am not positive, but I think this is just a North American glitch (UL/CSA).I think internationally you could make the justification that Rich pointed out that it is inherently safe and on these products skip a final AC hipot. So what if line and neutral are shorted to ground (other than for functionality reasons). The MOV's will short the line and neutral to ground at a couple hundred volts anyway and could fail short permanently. If it is the case that internationally it isn't a problem, yet somehow domestically it becomes a safety hazard only due to the follow-up services required ac hi-pot aspect, something seems wrong. It just doesn't seem to hold water from a technical basis. Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com -Original Message- From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: Thursday, December 16, 2010 8:17 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Here is another clunky suggestion. What if you put your Surge Suppressor circuit after a dual pole circuit breaker that is only energized when the device is powered up. That way, the VDR is out of the circuit during the Hipot test, but in-circuit during the Surge Immunity test. This brings up a good point in regards to production hipot testing. Some of our instruments have double pole relays, so during hipot those downstream circuits do not get tested. So those circuits have to be individually hipot tested before the side panels are installed. As you said, this goes against the intent of the production hipot test, but what else can you do? You do the best you can. If an inspector disagrees, have him give you the solution. The Other Brian -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of JIM WIESE Sent: Wednesday, December 15, 2010 5:18 PM To: ri...@ieee.org Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Thanks Rich, Your first paragraph is what I tried with the safety lab to no avail as they still required a factory hipot, which requires disassembly or some other form of clunky workaround as Brian mentioned. Brian's method could be feasible in some cases from the safety perspective to remove the MOV for the hipot, but lousy if you need a low impedance reliable path for thousands of amps of lightning current. It also is not feasible in most cases for potted or OSP sealed telecom equipment. Merry Christmas, Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com -Original Message- From: Richard Nute [mailto:rn...@san.rr.com] Sent: Wednesday, December 15, 2010 4:06 PM To: JIM WIESE Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Hi Jim: If the equipment is permanently grounded, then you can put in a VDR/MOV between mains and ground. Think of a permanent ground as a reinforced safeguard, with no need for basic insulation (in my opinion). For cord-connected equipment, IEC 62368-1 will likely require a series circuit of VDR and gas discharge tube. The big problem with VDR/MOVs is that we don't know the energy that must be dissipated by the VDR/MOV. If the energy is high enough, the VDR/MOV will be destroyed and you will have arcs to ground. Have a Merry Christmas! Rich On 12/15/2010 13:06, JIM WIESE wrote: > Hey Rich, > > The reason for VDR's (MOV's) to ground is to prevent arcing to the > chassis for customers that demand either 6KV or 10KV lightning tests. > The products are permanently grounded so the arcing to ground is not a > safety hazard at those levels. The products easily pass the hipot > without the MOV's to several KV (well above the hipot level). > > The arcing at 6 or 10KV often functionally kills the supply or other > circuitry, which of course 60950 could not care less about > functionality. But other standards do. > > It sounds like IEC 62368 will mess up using MOV's to ground though as I > am not aware of MOV's rated several KV. > > Best regards, > > Jim > > Jim Wiese > Senior Compliance Engineer > ADTRAN, Inc. > 901 Explorer Blvd. > Huntsville, AL 35806 > 256-963-8431 > 256-714-5882 (cell) > 256-963-6218 (fax) > jim.wi...@adtran.com > > > -Original Message- > From: Richard Nute [mailto:rn...@san.rr.com] > Sent: Wednesday, December 15, 2010 2:01 PM > To: JIM WIESE > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Here is another clunky suggestion. What if you put your Surge Suppressor circuit after a dual pole circuit breaker that is only energized when the device is powered up. That way, the VDR is out of the circuit during the Hipot test, but in-circuit during the Surge Immunity test. This brings up a good point in regards to production hipot testing. Some of our instruments have double pole relays, so during hipot those downstream circuits do not get tested. So those circuits have to be individually hipot tested before the side panels are installed. As you said, this goes against the intent of the production hipot test, but what else can you do? You do the best you can. If an inspector disagrees, have him give you the solution. The Other Brian -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of JIM WIESE Sent: Wednesday, December 15, 2010 5:18 PM To: ri...@ieee.org Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Thanks Rich, Your first paragraph is what I tried with the safety lab to no avail as they still required a factory hipot, which requires disassembly or some other form of clunky workaround as Brian mentioned. Brian's method could be feasible in some cases from the safety perspective to remove the MOV for the hipot, but lousy if you need a low impedance reliable path for thousands of amps of lightning current. It also is not feasible in most cases for potted or OSP sealed telecom equipment. Merry Christmas, Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com -Original Message- From: Richard Nute [mailto:rn...@san.rr.com] Sent: Wednesday, December 15, 2010 4:06 PM To: JIM WIESE Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Hi Jim: If the equipment is permanently grounded, then you can put in a VDR/MOV between mains and ground. Think of a permanent ground as a reinforced safeguard, with no need for basic insulation (in my opinion). For cord-connected equipment, IEC 62368-1 will likely require a series circuit of VDR and gas discharge tube. The big problem with VDR/MOVs is that we don't know the energy that must be dissipated by the VDR/MOV. If the energy is high enough, the VDR/MOV will be destroyed and you will have arcs to ground. Have a Merry Christmas! Rich On 12/15/2010 13:06, JIM WIESE wrote: > Hey Rich, > > The reason for VDR's (MOV's) to ground is to prevent arcing to the > chassis for customers that demand either 6KV or 10KV lightning tests. > The products are permanently grounded so the arcing to ground is not a > safety hazard at those levels. The products easily pass the hipot > without the MOV's to several KV (well above the hipot level). > > The arcing at 6 or 10KV often functionally kills the supply or other > circuitry, which of course 60950 could not care less about > functionality. But other standards do. > > It sounds like IEC 62368 will mess up using MOV's to ground though as I > am not aware of MOV's rated several KV. > > Best regards, > > Jim > > Jim Wiese > Senior Compliance Engineer > ADTRAN, Inc. > 901 Explorer Blvd. > Huntsville, AL 35806 > 256-963-8431 > 256-714-5882 (cell) > 256-963-6218 (fax) > jim.wi...@adtran.com > > > -Original Message- > From: Richard Nute [mailto:rn...@san.rr.com] > Sent: Wednesday, December 15, 2010 2:01 PM > To: JIM WIESE > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and > VDR bridging basic insulation. > > > > Hi Jim: > > > Thanks for your remarks. > > You CAN remove the VDR during hi-pot testing. > This is specified in 5.2.2: > > "To avoid damage to components or insulation > that are not involved in the test, > disconnection of integrated circuits or the > like and the use of equipotential bonding are > permitted." > > This is for the "type" test, not the "routine" > test. Nevertheless, your point is well taken. > > Also note that 5.2.1 specifies: > > "The electric strength of the SOLID INSULATION > used in the equipment shall be adequate." > > So, the hi-pot test only applies to solid > insulation. > > The other option is to specify the VDR at a higher > voltage than the hi-pot test voltage. > > Regarding VDRs, I don't know why any equipment > would need a VDR between mains and earth. The > requirements for clearance, creepage, and solid > insulations require an electric strength at least >
Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
I found this in UL 60950, clause 1.5.9.1: -- quote --- If a surge suppressor is used in a PRIMARY CIRCUIT, it shall be a VDR and it shall comply with Annex Q. NOTE 1 A VDR is sometimes referred to as a varistor or a metal oxide varistor (MOV). Devices such as gas discharge tubes, carbon blocks and semiconductor devices with non-linear voltage/current characteristics are not considered as VDRs in this standard. --- end quote --- This sounds like it prevents the use of VDR/gas discharge tube combinations to limit primary-to-earth line surges, or gas discharge tubes in the primary completely. Is this correct? I'll bet the gas tube companies are having heartburn over this. Pat Lawler EMC Engineer SL Power Electronics Corp. ri...@ieee.org wrote on 12/15/2010 12:05:18 PM: > On 12/15/2010 11:41, Kunde, Brian wrote: > > Does it make VDRs safer to use them in series with a gas-tube like some > > do with Varistors? > Hi Brian: > > Yes. > Today, this is the trend among manufacturers that > want to use a VDR between mains and earth. > And, TC108 is still trying to sort out the requirements > for both devices in such a circuit. > > Best wishes for a Merry Christmas, > 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 > All emc-pstc postings are archived and searchable on the web at: > http://product-compliance.oc.ieee.org/ > Graphics (in well-used formats), large files, etc. can be posted to that URL. > Website: http://www.ieee-pses.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 > Mike Cantwell > For policy questions, send mail to: > Jim Bacher: > David Heald: - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Thanks Rich, Your first paragraph is what I tried with the safety lab to no avail as they still required a factory hipot, which requires disassembly or some other form of clunky workaround as Brian mentioned. Brian's method could be feasible in some cases from the safety perspective to remove the MOV for the hipot, but lousy if you need a low impedance reliable path for thousands of amps of lightning current. It also is not feasible in most cases for potted or OSP sealed telecom equipment. Merry Christmas, Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com -Original Message- From: Richard Nute [mailto:rn...@san.rr.com] Sent: Wednesday, December 15, 2010 4:06 PM To: JIM WIESE Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Hi Jim: If the equipment is permanently grounded, then you can put in a VDR/MOV between mains and ground. Think of a permanent ground as a reinforced safeguard, with no need for basic insulation (in my opinion). For cord-connected equipment, IEC 62368-1 will likely require a series circuit of VDR and gas discharge tube. The big problem with VDR/MOVs is that we don't know the energy that must be dissipated by the VDR/MOV. If the energy is high enough, the VDR/MOV will be destroyed and you will have arcs to ground. Have a Merry Christmas! Rich On 12/15/2010 13:06, JIM WIESE wrote: > Hey Rich, > > The reason for VDR's (MOV's) to ground is to prevent arcing to the > chassis for customers that demand either 6KV or 10KV lightning tests. > The products are permanently grounded so the arcing to ground is not a > safety hazard at those levels. The products easily pass the hipot > without the MOV's to several KV (well above the hipot level). > > The arcing at 6 or 10KV often functionally kills the supply or other > circuitry, which of course 60950 could not care less about > functionality. But other standards do. > > It sounds like IEC 62368 will mess up using MOV's to ground though as I > am not aware of MOV's rated several KV. > > Best regards, > > Jim > > Jim Wiese > Senior Compliance Engineer > ADTRAN, Inc. > 901 Explorer Blvd. > Huntsville, AL 35806 > 256-963-8431 > 256-714-5882 (cell) > 256-963-6218 (fax) > jim.wi...@adtran.com > > > -Original Message- > From: Richard Nute [mailto:rn...@san.rr.com] > Sent: Wednesday, December 15, 2010 2:01 PM > To: JIM WIESE > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and > VDR bridging basic insulation. > > > > Hi Jim: > > > Thanks for your remarks. > > You CAN remove the VDR during hi-pot testing. > This is specified in 5.2.2: > > "To avoid damage to components or insulation > that are not involved in the test, > disconnection of integrated circuits or the > like and the use of equipotential bonding are > permitted." > > This is for the "type" test, not the "routine" > test. Nevertheless, your point is well taken. > > Also note that 5.2.1 specifies: > > "The electric strength of the SOLID INSULATION > used in the equipment shall be adequate." > > So, the hi-pot test only applies to solid > insulation. > > The other option is to specify the VDR at a higher > voltage than the hi-pot test voltage. > > Regarding VDRs, I don't know why any equipment > would need a VDR between mains and earth. The > requirements for clearance, creepage, and solid > insulations require an electric strength at least > as great as the expected transient overvoltage, > regardless whether a VDR is between mains and > earth or not. So, the VDR does not protect > anything against any voltage up to the required > electric strength of the equipment. > > The VDR *may* be useful to protect against > transient voltages exceeding the required electric > strength.n which case it will pass the hi-pot > test. > > In the new IEC 62368, the requirement is that any > VDR between mains and earth shall be rated greater > than the required electric strength. > > > Best wishes for the Christmas season, > 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Hi Jim: If the equipment is permanently grounded, then you can put in a VDR/MOV between mains and ground. Think of a permanent ground as a reinforced safeguard, with no need for basic insulation (in my opinion). For cord-connected equipment, IEC 62368-1 will likely require a series circuit of VDR and gas discharge tube. The big problem with VDR/MOVs is that we don't know the energy that must be dissipated by the VDR/MOV. If the energy is high enough, the VDR/MOV will be destroyed and you will have arcs to ground. Have a Merry Christmas! Rich On 12/15/2010 13:06, JIM WIESE wrote: > Hey Rich, > > The reason for VDR's (MOV's) to ground is to prevent arcing to the > chassis for customers that demand either 6KV or 10KV lightning tests. > The products are permanently grounded so the arcing to ground is not a > safety hazard at those levels. The products easily pass the hipot > without the MOV's to several KV (well above the hipot level). > > The arcing at 6 or 10KV often functionally kills the supply or other > circuitry, which of course 60950 could not care less about > functionality. But other standards do. > > It sounds like IEC 62368 will mess up using MOV's to ground though as I > am not aware of MOV's rated several KV. > > Best regards, > > Jim > > Jim Wiese > Senior Compliance Engineer > ADTRAN, Inc. > 901 Explorer Blvd. > Huntsville, AL 35806 > 256-963-8431 > 256-714-5882 (cell) > 256-963-6218 (fax) > jim.wi...@adtran.com > > > -Original Message- > From: Richard Nute [mailto:rn...@san.rr.com] > Sent: Wednesday, December 15, 2010 2:01 PM > To: JIM WIESE > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and > VDR bridging basic insulation. > > > > Hi Jim: > > > Thanks for your remarks. > > You CAN remove the VDR during hi-pot testing. > This is specified in 5.2.2: > > "To avoid damage to components or insulation > that are not involved in the test, > disconnection of integrated circuits or the > like and the use of equipotential bonding are > permitted." > > This is for the "type" test, not the "routine" > test. Nevertheless, your point is well taken. > > Also note that 5.2.1 specifies: > > "The electric strength of the SOLID INSULATION > used in the equipment shall be adequate." > > So, the hi-pot test only applies to solid > insulation. > > The other option is to specify the VDR at a higher > voltage than the hi-pot test voltage. > > Regarding VDRs, I don't know why any equipment > would need a VDR between mains and earth. The > requirements for clearance, creepage, and solid > insulations require an electric strength at least > as great as the expected transient overvoltage, > regardless whether a VDR is between mains and > earth or not. So, the VDR does not protect > anything against any voltage up to the required > electric strength of the equipment. > > The VDR *may* be useful to protect against > transient voltages exceeding the required electric > strength.n which case it will pass the hi-pot > test. > > In the new IEC 62368, the requirement is that any > VDR between mains and earth shall be rated greater > than the required electric strength. > > > Best wishes for the Christmas season, > 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Hi Brian: You describe the problem accurately. The VDR will start conducting before the required test voltage is reached. From a safety point of view, this is not acceptable unless the equipment is reliably grounded. From a functional point of view, this is the intended performance. Let's put it this way. Normal mains voltage is comprised of two elements: mains operating voltage; mains transient voltage. The safety of the equipment is dependent upon the mains insulation (between mains and accessible parts, including ground) being able to withstand both voltages. As near as I can discern, surge immunity is the same as mains transient withstand. Surge immunity implies withstanding a 1.2x50 impulse waveform, while mains transient withstand implies a sinewave. (The mains transient withstand test can be done with a sinewave, DC, or a 1.2x50 impulse.) The IEC 62368-1 requirement is that EVERYTHING connected between mains and earth must pass a dielectric withstand test. Have a Merry Christmas, Rich On 12/15/2010 12:33, Brian O'Connell wrote: > The problem with the VDR being rated for a level 3 surge, which is significantly greater than the typical test V for BI, is that the VDR will typically start conducting long before required test voltage is reached. > > Di-electric withstand and surge immunity are very different animals. > > I saw a VDR from line to chassis in a competitor's component P/S - never understood the reason for this construction. > > Is the VDR rating for 62368 conformity a working voltage or surge rating ? > > Brian > - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Hey Rich, The reason for VDR's (MOV's) to ground is to prevent arcing to the chassis for customers that demand either 6KV or 10KV lightning tests. The products are permanently grounded so the arcing to ground is not a safety hazard at those levels. The products easily pass the hipot without the MOV's to several KV (well above the hipot level). The arcing at 6 or 10KV often functionally kills the supply or other circuitry, which of course 60950 could not care less about functionality. But other standards do. It sounds like IEC 62368 will mess up using MOV's to ground though as I am not aware of MOV's rated several KV. Best regards, Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com -Original Message- From: Richard Nute [mailto:rn...@san.rr.com] Sent: Wednesday, December 15, 2010 2:01 PM To: JIM WIESE Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Hi Jim: Thanks for your remarks. You CAN remove the VDR during hi-pot testing. This is specified in 5.2.2: "To avoid damage to components or insulation that are not involved in the test, disconnection of integrated circuits or the like and the use of equipotential bonding are permitted." This is for the "type" test, not the "routine" test. Nevertheless, your point is well taken. Also note that 5.2.1 specifies: "The electric strength of the SOLID INSULATION used in the equipment shall be adequate." So, the hi-pot test only applies to solid insulation. The other option is to specify the VDR at a higher voltage than the hi-pot test voltage. Regarding VDRs, I don't know why any equipment would need a VDR between mains and earth. The requirements for clearance, creepage, and solid insulations require an electric strength at least as great as the expected transient overvoltage, regardless whether a VDR is between mains and earth or not. So, the VDR does not protect anything against any voltage up to the required electric strength of the equipment. The VDR *may* be useful to protect against transient voltages exceeding the required electric strength.n which case it will pass the hi-pot test. In the new IEC 62368, the requirement is that any VDR between mains and earth shall be rated greater than the required electric strength. Best wishes for the Christmas season, Rich On 12/15/2010 11:27, JIM WIESE wrote: > Rich, > > The issue we ran into with this is that UL and other NRTL's require > factory hi-pot testing on AC interfaces as part of follow-up services. > The product will obviously fail at that point. The original 60950-1 > safety testing is done with the VDR's removed. But for the factory > hi-pot the VDR's often cannot be removed without disassembly of the > product, and even if they could be removed it violates the intent of the > test, which is to perform the factory hi-pot right before it is boxed up > for shipping, not rip it apart, do a hipot, and then re-assemble the > product. > > As you point out the conditions necessary to allow the VDR's to ground > in the first place already require the assumption that the VDR can go > short and not create a hazard. > > So 60950-1 now allows the VDR's to ground, but the follow-up services > and listing requirements for the factory hi-pot here in the US and > Canada more or less prevent doing it. > > So, there should be some kind of waiver from the factory hi-pot if the > product has VDR's to ground as permitted in 60950-1, but unless that > happens it is silly to allow it in the UL/CSA version, unless people > feel tearing a product apart to disable VDR's, then doing a hi-pot, then > reassembling the equipment makes sense. > > Best regards, > > Jim > > Jim Wiese > Senior Compliance Engineer > ADTRAN, Inc. > 901 Explorer Blvd. > Huntsville, AL 35806 > 256-963-8431 > 256-714-5882 (cell) > 256-963-6218 (fax) > jim.wi...@adtran.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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
In EMC are testing to 2 kV surge. But Brazil deemed our product "telecom" and
applied 4 kV. A couple of our products spark and arc impressively and
continue running. A couple of others quit, died, castors up, and the smoke
got out... (It fun when they do that!)
EMC says it has to continue to work.
Safety says it only has to fail safely.
Engineering says fix it but don't change anything.
VDR between line and earth,
and between line to line fixes it to 4 kV.
But I run right into the safety guy and all these notes, about pluggable,
single/double fused, screwed down earths, permanent connect, etc.
Bill
In the event of a national emergency,
click on the following links to provide directions to your duly elected
mis-representatives.
http://www.usa.gov/Contact/Elected.shtml
or...
https://writerep.house.gov/writerep/welcome.shtml
http://www.senate.gov/general/contact_information/senators_cfm.cfm
if really desperate...
http://www.usa.gov/Contact/Elected.shtml
--- On Wed, 12/15/10, Brian O'Connell wrote:
From: Brian O'Connell
Subject: RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and
VDR
bridging basic insulation.
To: EMC-PSTC@LISTSERV.IEEE.ORG
Date: Wednesday, December 15, 2010, 3:33 PM
The problem with the VDR being rated for a level 3 surge, which is
significantly greater than the typical test V for BI, is that the VDR will
typically start conducting long before required test voltage is reached.
Di-electric withstand and surge immunity are very different animals.
I saw a VDR from line to chassis in a competitor's component P/S - never
understood the reason for this construction.
Is the VDR rating for 62368 conformity a working voltage or surge
rating ?
Brian
> -Original Message-
> From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf
> Of Richard
> Nute
> Sent: Wednesday, December 15, 2010 12:01 PM
> To: JIM WIESE
> Cc: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and
> VDR bridging basic insulation.
>
>
> Hi Jim:
>
> Thanks for your remarks.
>
> You CAN remove the VDR during hi-pot testing.
> This is specified in 5.2.2:
>
> "To avoid damage to components or insulation
> that are not involved in the test,
> disconnection of integrated circuits or the
> like and the use of equipotential bonding are
> permitted."
>
> This is for the "type" test, not the "routine"
> test. Nevertheless, your point is well taken.
>
> Also note that 5.2.1 specifies:
>
> "The electric strength of the SOLID INSULATION
> used in the equipment shall be adequate."
>
> So, the hi-pot test only applies to solid
> insulation.
>
> The other option is to specify the VDR at a higher
> voltage than the hi-pot test voltage.
>
> Regarding VDRs, I don't know why any equipment
> would need a VDR between mains and earth. The
> requirements for clearance, creepage, and solid
> insulations require an electric strength at least
> as great as the expected transient overvoltage,
> regardless whether a VDR is between mains and
> earth or not. So, the VDR does not protect
> anything against any voltage up to the required
> electric strength of the equipment.
>
> The VDR *may* be useful to protect against
> transient voltages exceeding the required electric
> strength.n which case it will pass the hi-pot
> test.
>
> In the new IEC 62368, the requirement is that any
> VDR between mains and earth shall be rated greater
> than the required electric strength.
>
>
> Best wishes for the Christmas season,
> 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
All emc-pstc postings are archived and searchable on the web at:
http://product-compliance.oc.ieee.org/
Graphics (in well-used formats), large files, etc. can be posted to
that URL.
Website: http://www.ieee-pses.org/
Instructions: http://listse
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
The problem with the VDR being rated for a level 3 surge, which is significantly greater than the typical test V for BI, is that the VDR will typically start conducting long before required test voltage is reached. Di-electric withstand and surge immunity are very different animals. I saw a VDR from line to chassis in a competitor's component P/S - never understood the reason for this construction. Is the VDR rating for 62368 conformity a working voltage or surge rating ? Brian > -Original Message- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf > Of Richard > Nute > Sent: Wednesday, December 15, 2010 12:01 PM > To: JIM WIESE > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and > VDR bridging basic insulation. > > > Hi Jim: > > Thanks for your remarks. > > You CAN remove the VDR during hi-pot testing. > This is specified in 5.2.2: > > "To avoid damage to components or insulation > that are not involved in the test, > disconnection of integrated circuits or the > like and the use of equipotential bonding are > permitted." > > This is for the "type" test, not the "routine" > test. Nevertheless, your point is well taken. > > Also note that 5.2.1 specifies: > > "The electric strength of the SOLID INSULATION > used in the equipment shall be adequate." > > So, the hi-pot test only applies to solid > insulation. > > The other option is to specify the VDR at a higher > voltage than the hi-pot test voltage. > > Regarding VDRs, I don't know why any equipment > would need a VDR between mains and earth. The > requirements for clearance, creepage, and solid > insulations require an electric strength at least > as great as the expected transient overvoltage, > regardless whether a VDR is between mains and > earth or not. So, the VDR does not protect > anything against any voltage up to the required > electric strength of the equipment. > > The VDR *may* be useful to protect against > transient voltages exceeding the required electric > strength.n which case it will pass the hi-pot > test. > > In the new IEC 62368, the requirement is that any > VDR between mains and earth shall be rated greater > than the required electric strength. > > > Best wishes for the Christmas season, > 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
On 12/15/2010 11:41, Kunde, Brian wrote: > Does it make VDRs safer to use them in series with a gas-tube like some > do with Varistors? Hi Brian: Yes. Today, this is the trend among manufacturers that want to use a VDR between mains and earth. And, TC108 is still trying to sort out the requirements for both devices in such a circuit. Best wishes for a Merry Christmas, 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Hi Jim: Thanks for your remarks. You CAN remove the VDR during hi-pot testing. This is specified in 5.2.2: "To avoid damage to components or insulation that are not involved in the test, disconnection of integrated circuits or the like and the use of equipotential bonding are permitted." This is for the "type" test, not the "routine" test. Nevertheless, your point is well taken. Also note that 5.2.1 specifies: "The electric strength of the SOLID INSULATION used in the equipment shall be adequate." So, the hi-pot test only applies to solid insulation. The other option is to specify the VDR at a higher voltage than the hi-pot test voltage. Regarding VDRs, I don't know why any equipment would need a VDR between mains and earth. The requirements for clearance, creepage, and solid insulations require an electric strength at least as great as the expected transient overvoltage, regardless whether a VDR is between mains and earth or not. So, the VDR does not protect anything against any voltage up to the required electric strength of the equipment. The VDR *may* be useful to protect against transient voltages exceeding the required electric strength.n which case it will pass the hi-pot test. In the new IEC 62368, the requirement is that any VDR between mains and earth shall be rated greater than the required electric strength. Best wishes for the Christmas season, Rich On 12/15/2010 11:27, JIM WIESE wrote: > Rich, > > The issue we ran into with this is that UL and other NRTL's require > factory hi-pot testing on AC interfaces as part of follow-up services. > The product will obviously fail at that point. The original 60950-1 > safety testing is done with the VDR's removed. But for the factory > hi-pot the VDR's often cannot be removed without disassembly of the > product, and even if they could be removed it violates the intent of the > test, which is to perform the factory hi-pot right before it is boxed up > for shipping, not rip it apart, do a hipot, and then re-assemble the > product. > > As you point out the conditions necessary to allow the VDR's to ground > in the first place already require the assumption that the VDR can go > short and not create a hazard. > > So 60950-1 now allows the VDR's to ground, but the follow-up services > and listing requirements for the factory hi-pot here in the US and > Canada more or less prevent doing it. > > So, there should be some kind of waiver from the factory hi-pot if the > product has VDR's to ground as permitted in 60950-1, but unless that > happens it is silly to allow it in the UL/CSA version, unless people > feel tearing a product apart to disable VDR's, then doing a hi-pot, then > reassembling the equipment makes sense. > > Best regards, > > Jim > > Jim Wiese > Senior Compliance Engineer > ADTRAN, Inc. > 901 Explorer Blvd. > Huntsville, AL 35806 > 256-963-8431 > 256-714-5882 (cell) > 256-963-6218 (fax) > jim.wi...@adtran.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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Does it make VDRs safer to use them in series with a gas-tube like some do with Varistors? I've never seen it done but I was told years ago that some companies have a screw in the back of their products that connects the chassis/earth ground connection to their surge suppression circuit. The screw is removed to break the ground point during the hipot test, then reinstalled after the test. The Other Brian -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of JIM WIESE Sent: Wednesday, December 15, 2010 2:28 PM To: ri...@ieee.org; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Rich, The issue we ran into with this is that UL and other NRTL's require factory hi-pot testing on AC interfaces as part of follow-up services. The product will obviously fail at that point. The original 60950-1 safety testing is done with the VDR's removed. But for the factory hi-pot the VDR's often cannot be removed without disassembly of the product, and even if they could be removed it violates the intent of the test, which is to perform the factory hi-pot right before it is boxed up for shipping, not rip it apart, do a hipot, and then re-assemble the product. As you point out the conditions necessary to allow the VDR's to ground in the first place already require the assumption that the VDR can go short and not create a hazard. So 60950-1 now allows the VDR's to ground, but the follow-up services and listing requirements for the factory hi-pot here in the US and Canada more or less prevent doing it. So, there should be some kind of waiver from the factory hi-pot if the product has VDR's to ground as permitted in 60950-1, but unless that happens it is silly to allow it in the UL/CSA version, unless people feel tearing a product apart to disable VDR's, then doing a hi-pot, then reassembling the equipment makes sense. Best regards, Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com -Original Message- From: Richard Nute [mailto:rn...@san.rr.com] Sent: Wednesday, December 15, 2010 1:02 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Hi Donald: A VDR is taken as a device that is likely to fail. If the VDR is connected between mains and the protective earthing system, then the PE system must be considered reliable, that is, equivalent to a reinforced safeguard. Ever since the days of 2-wire plugs and sockets, grounding by means of a domestic plug and socket has not been considered reliable (because you could not predict whether the installation was 2-wire or 2-wire plus ground). In order to have a reliable ground, the ground construction must be permanent or equivalent. (Equivalent is taken as by means of industrial- grade plug and socket schemes.) 1.5.9.4 specifies the equivalent grounding schemes. Yes, you are correct in that a VDR is not permitted to be connected to earth (ground) in pluggable equipment type A. Best wishes for a Merry Christmas, Richard Nute Product Safety Consultant San Diego On 12/14/2010 14:20, Donald McElheran wrote: > All: > > Under clause 1.5.9.4 "Bridging of basic insulation by a VDR" in the > latest version of 60950-1 > > Paragraph two: > > "Equipment with such a VDR bridging insulation shall be one of the > following: > > - equipment that has the provision for a permanently > connected PROTECTIVE EARTHING CONNECTOR and is provided with > instructions for the installation of that conductor. > > > This requirement appears to rule out the use of power supplies making > use of earthed VDRs in their primary circuits, if used in "Pluggable > Equipment Type A" if a separate earthing terminal is not provided. > > Could anyone confirm that this interpretion is correct and wether this > was the intent of the committee. > > Donald McElheran > Product Compliance Specialist > Ross Video | Live Production Technology > www.rossvideo.com > +1 (613) 652-4886 > - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send
RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation.
Rich, The issue we ran into with this is that UL and other NRTL's require factory hi-pot testing on AC interfaces as part of follow-up services. The product will obviously fail at that point. The original 60950-1 safety testing is done with the VDR's removed. But for the factory hi-pot the VDR's often cannot be removed without disassembly of the product, and even if they could be removed it violates the intent of the test, which is to perform the factory hi-pot right before it is boxed up for shipping, not rip it apart, do a hipot, and then re-assemble the product. As you point out the conditions necessary to allow the VDR's to ground in the first place already require the assumption that the VDR can go short and not create a hazard. So 60950-1 now allows the VDR's to ground, but the follow-up services and listing requirements for the factory hi-pot here in the US and Canada more or less prevent doing it. So, there should be some kind of waiver from the factory hi-pot if the product has VDR's to ground as permitted in 60950-1, but unless that happens it is silly to allow it in the UL/CSA version, unless people feel tearing a product apart to disable VDR's, then doing a hi-pot, then reassembling the equipment makes sense. Best regards, Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com -Original Message- From: Richard Nute [mailto:rn...@san.rr.com] Sent: Wednesday, December 15, 2010 1:02 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. Hi Donald: A VDR is taken as a device that is likely to fail. If the VDR is connected between mains and the protective earthing system, then the PE system must be considered reliable, that is, equivalent to a reinforced safeguard. Ever since the days of 2-wire plugs and sockets, grounding by means of a domestic plug and socket has not been considered reliable (because you could not predict whether the installation was 2-wire or 2-wire plus ground). In order to have a reliable ground, the ground construction must be permanent or equivalent. (Equivalent is taken as by means of industrial- grade plug and socket schemes.) 1.5.9.4 specifies the equivalent grounding schemes. Yes, you are correct in that a VDR is not permitted to be connected to earth (ground) in pluggable equipment type A. Best wishes for a Merry Christmas, Richard Nute Product Safety Consultant San Diego On 12/14/2010 14:20, Donald McElheran wrote: > All: > > Under clause 1.5.9.4 "Bridging of basic insulation by a VDR" in the > latest version of 60950-1 > > Paragraph two: > > "Equipment with such a VDR bridging insulation shall be one of the > following: > > - equipment that has the provision for a permanently > connected PROTECTIVE EARTHING CONNECTOR and is provided with > instructions for the installation of that conductor. > > > This requirement appears to rule out the use of power supplies making > use of earthed VDRs in their primary circuits, if used in "Pluggable > Equipment Type A" if a separate earthing terminal is not provided. > > Could anyone confirm that this interpretion is correct and wether this > was the intent of the committee. > > Donald McElheran > Product Compliance Specialist > Ross Video | Live Production Technology > www.rossvideo.com > +1 (613) 652-4886 > - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - 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 All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
