Hi Muriel and group, Hope you all had a good Christmas. Yes, As Chris mentions, there can be problems with coupling/de-coupling networks. A classic example is the T-ISNs for conducted emissions on telecommunication lines as per the new EN55022 : 1998 The mains LISN however causing problems is not that common. For Mil Stds tests current probes are normally used, but only for a few type of tests (like DC and other leads), where the de-coupling device is still a LISN or a 10 micro Farad feed through Capacitor. Mains supply units are still tested with LISNs. But these are 5 micro henry LISNs. And the test set ups are quite different. The LISN tests are more reliable and repeatable than the current probe tests.
Happy New Year. The real new Millenium. Praveen rao -----Original Message----- From: Muriel Bittencourt de Liz [mailto:mur...@grucad.ufsc.br] Sent: Saturday, 23 December 2000 3:05 AM To: Lista de EMC da IEEE Subject: Doubt with conducted emissions measurement Hello Group! First of all, I wish a merry christmas and a happy new year for the list members. Second, I'd like to solve a doubt. It concerns the methodology of conducted emissions tests. Let's suppose a power electronic equipment (static converter) that has a boost converter in the entrance that's used for power factor correction (PFC). When I make a conducted emissions test, I plug the converter in a LISN, then I plug the LISN in the outlet, this way (the classical way): Equipment => LISN => Outlet (Mains) Well, the LISN consists of a RLC network that has the purposes of: - prevent that external interference from the mains contaminate the measurement - create a stabilized impedance (50 ohms) in the frequency range of interest (150kHz-30MHz) to make results repeatable, from site to site. Ok, what I've said until here is well known and is present in every book about this subject of EMC. My doubt is this: The LISN can't interfere in the functional operation of the converter? Things like resonance, extra ripple can't occur? And, imagining the worst scenario, can the LISN make my equipment not work according to what's expected? Another thing I was thinking about is the fact that the military tests os conducted emissions are done with a probe, and not using a LISN. I'm very curious about this subject because I was asked about this question and I became very surprised, because I have never thought about this. We are, generally, so interested in results that we forget to ask the "basic questions" sometimes. Well, I think that's all. Thanks in advance for those who can help me. Best Regards %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Eng. Muriel Bittencourt de Liz EMC Testing and Troubleshooting Group of Conception and Analysis of Electromagnetic Devices Federal University at Santa Catarina Florianópolis, SC, Brazil ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
