Hi Larry:
Are the failures do to actual damage, or just to upset? I can imagine some situations where there might be upset for the one-at-a-time configuration you describe, and I can understand how someone might argue this configuration is not an appropriate test configuration. However, I can't think of a valid reason why actual damage could be caused when using this test configuration. Also, during the one-at-a-time testing, how are the unused power cords terminated? Lastly, does the system perform its intended function when portions of the system are unpowered? Just some food for thought. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) <mailto:j...@randolph-telecom.com> j...@randolph-telecom.com <http://www.randolph-telecom.com> http://www.randolph-telecom.com From: Larry K. Stillings [mailto:la...@complianceworldwide.com] Sent: Wednesday, January 02, 2019 5:16 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] IEC 61000-4-5 Surge Testing Single plug vs. multiple plug system All, I received the following email from a customer today via their customer addressing our application of surge testing. We are testing laboratory equipment per IEC/EN 61326-1 and IEC/EN 61326-2-6 and specifically are having failures with respect to surge on a system that has multiple power cords. We are testing one power cord at a time. Here are their comments we have never tested a system comprised of multiple instruments in this way before. i.e. applying surge to one unit at a time - we have always, with agreement from our customers, applied surge (and in fact all tests) to all of the units plugged into e.g. a mains distribution block all at the same time. Especially for surge, it seems unlikely that in the real world any real surge on the mains supply would not affect all things in a system as it is very likely they are all plugged into the same mains circuit in e.g a particular room. To further bolster this, we have made comment to customers in the past that it could be noted in the manual to ensure this is the case. By applying surge to all units at the same time, we maintain all of their supply voltages at the same level. I can see how, by applying a surge to a single part of the wider system, communications issues could occur as suddenly the points of reference (i.e. reference voltages) for different parts of the system could be pulled away from each other by the surge. Testing a system by applying the tests to all at once, rather than a single item at a time, isn't necessarily an "easy way out" either. For other tests e.g. conducted emissions, where noise transmitted from the unit under test back onto the mains supply is measured, passing is made more difficult by measuring all units at once. Where in this case one at a time would be much more favourable. Our test house has always advised that we can choose, either all tests one at a time, or all tests applied to all through a mains block, but we cannot mix and match between different sections for the conducted EMC tests. I know this brings up all sorts of questions, however I would like to focus on the surge testing at the moment. I am pretty sure at least one of the standards says conducted emissions shall be tested on each port individually, but we don't need to go there right now ;-) Thoughts when you get responses like this? Larry K. Stillings Compliance Worldwide, Inc. Test Locally, Sell Globally and Launch Your Products Around the World! 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