Depending on the impedance of the EUT and the impedance between N and PE of the CDN more than 1,5kV may be seen between L and N when applying this surge of 2kV between L and PE. This could also be demonstrated by measurements. This has nothing to do with referencing the output of the power supply to ground. A lightning stroke does not know if a unit with 3pole plug (with PE) or with 2pole plug (without PE) is connected to the wall outlet. So in my opinion this surge test between L and PE and between N and PE should be done in any case also for such class 2 power supply units with double insulation as evidence for a certain degree of immunity. Our experience showed that such a class 2 power supply from a far east manufacturer failed this surge test with 2kV from L to PE with damaged input rectifiers. Helmut Koester
-----Ursprüngliche Nachricht----- Von: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Im Auftrag von Bob Richards Gesendet: Montag, 11. März 2013 17:48 An: ieee Betreff: Re: [PSES] Surge Test Power Supply Class 2 acc. EN61000-4-5 Even without a return path for the surge that is performed Line or Neutral relative to PE (with no PE terminal on the EUT) there will be a large surge voltage between Line-Neutral. If surging at 2kv L-PE, there may be as much as 1.3kv between L-N. It has to do with the design of the CDN. This will exceed the normal 1kV test level between L-N. I know, because I ran into a situation where a product failed, and investigation showed the above to be true. I thought at first it was a problem with the surge CDN, but found out it is the nature of the CDN when designed according to the standard's requirements. Bob R. From: Bill Owsley <wdows...@yahoo.com> To: Derek Walton <lfresea...@aol.com>; Anthony Thomson <ton...@europe.com> Cc: "EMC-PSTC@LISTSERV.IEEE.ORG" <EMC-PSTC@LISTSERV.IEEE.ORG> Sent: Friday, March 8, 2013 5:49 PM Subject: Re: [PSES] Surge Test Power Supply Class 2 acc. EN61000-4-5 If the EUT and test setup for it, has no PE ground, this should have been a null result, nothing would happen. But given that damage occurred, something faulted to PE ground, and that should not have happened. From: Derek Walton <lfresea...@aol.com> To: Anthony Thomson <ton...@europe.com> Cc: "EMC-PSTC@LISTSERV.IEEE.ORG" <EMC-PSTC@LISTSERV.IEEE.ORG> Sent: Friday, March 8, 2013 1:52 PM Subject: Re: [PSES] Surge Test Power Supply Class 2 acc. EN61000-4-5 Well folks. I disagree. Here's why. If the power supply is used in an application were the output is referenced to ground , you will not be stressing the primary to secondary circuits. If your power supply isn't man enough for this you should place warnings in your literature BEFORE purchase is made. MHO Derek Sent from my iPhone On Mar 8, 2013, at 9:00 AM, "Anthony Thomson" <ton...@europe.com> wrote: Table 4 of EN 55024 is clear enough, 1kV line-line and 2kV line-ground tested i.a.w. IEC 61000-4-5. Clause 7.2 of 61000-4-5 says that, for double insulated products without an earth, line-ground tests may be omitted. I would agree with your power supply manufacturer assuming the PSU is of double insulated construction. 1 kV is sufficient to claim compliance to '55024. T ----- Original Message ----- From: H.Köster Sent: 03/08/13 01:50 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Surge Test Power Supply Class 2 acc. EN61000-4-5 Hello group, I have a question about the surge test for a 27VA ac adapter (without PE and external earth connections) for IT equipment. EN55024 refers to EN61000-4-5 requiring a test level of 1kV between L and N and 2kV between L and PE as well as between N and PE. The power supply failed the common mode tests of 2kV with damages. The power supply manufacturer argues that the power supply has no PE connection and therefore these common mode tests are not required. Please give me your experts comments. Thanks Helmut Koester PSi Engineering GmbH mailto:h.koes...@psi-engineering.de - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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