Hello Larry, What is the intended end configuration? Is there one single external power cord from the system to the AC Mains? Or is it required that each individual instrument or component of the system be independently plugged into the AC Mains? I typically test each individual external power cord that are intended to go directly into the AC Mains. There were a couple configurations where I did not. In one case, It was a rack of test equipment that had a UPS, housed in the rack. This design's intent was to power the rack of equipment with the UPS and only one power cord directly into the AC Mains. The output of the UPS went to an AC distribution block internal to the rack where all the remaining Test equipment was plugged into. In this case surges where applied only to the UPS since there was only one external power cord which was the designs intent. The UPS was the source for powering the other equipment mounted in the rack. Another design was very similar where the end configuration of the device housed several independent systems or components. This design incorporated a couple high end computers, a 47 inch ultra-high brightness LCD, some hydraulics, relays, a light booth with multiple luminaire, and a couple 100 watt power supplies. This design's intent was to be plugged into the AC Mains with a single AC Power cord. The distribution of AC was internal and housed within the device. This device was surge tested in that same way as the rack. We also have design's or systems that have 2 or 3 external power cords and these of course are tested independently since end use intended configuration is to supply AC with multiple AC Main connections.
Regards, Mark From: Larry K. Stillings [mailto:[email protected]] Sent: Wednesday, January 2, 2019 5:16 PM To: [email protected] 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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