Hi all, I have a question that I re-hash every time I go through product testing. It has to do with EFT testing the AC mains port of a product.
Our EFT generator (Keytek CE Master) has a built in coupling/decoupling network which is capable of putting the EFT onto single lines (L1 to ref ground, L2 to ref ground or PE to ref ground). It also has the capability to couple the EFT onto any combinations of those lines. For instance, I can test L1 and L2 and PE to ref ground simultaneously, L1 and PE to ref ground...you get the picture? If I use all single line tests and all line combinations, I get 7 different tests for each polarity...a total of 14 tests at each voltage level. We test EFT in-house for the past couple of years. Before that, I had the testing done at two different labs. One lab insisted that we pass all single line tests as well as passing all combination tests. The other lab tests one line at a time... and that's it. Historically, I have tested all combinations...just because I can. Our EFT generator has automatic "Class" settings. If I use them, it performs the tests one line at a time...and that's it. I have read IEC 1000-4-4 and the Keytek transient testing handbook. Both are worded such that my understanding of what they are saying is... single line tests are all that is required. It makes a big difference. I can think of at least four instances where I have tested our products with passing results for the single line tests and failing results for the combination tests. Can anyone provide me with a sound explanation of two things: 1. Why does it seem as if single line tests are all that is required? (For instance, would real life EFTs only be on single lines.) 2. After explaining item 1 above, can somebody tell me what benefits I get by testing combinations of lines. (other than the mental exercise of wondering why). Thanks for your time guys/ladies and have a great weekend. Chris Maxwell | Design Engineer - Optical Division email [email protected] | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
