Virtually all commercially available EFT simulators with built-in coupler/decouplers for the ac mains contain the 33nF capacitors internally. The only reason you might need to use them externally is if you were building your own coupler/decoupler, which also includes the necessary backfilter components to allow voltages to be developed and to protect other equipment connected to the same mains.
I'm quite surprised by Schaffner's response to you.... According to their own literature, the Model NSG 3025 is designed to allow EFT tests to be run on live AC or DC mains using a built-in coupling network (this was taken from their web page some time ago -- the product seems to have been removed from their offering judging by their new web site design. At least I can't find it anymore.). Since IEC 61000-4-4 (and I believe all earlier versions) require the use of a 33nF coupling capacitor, I'd be amazed if they actually used a capacitor that was not in compliance with the standard. Also, from looking at a picture of the product, there is obviously an ac connector on the front panel -- I would assume to which you would connect the product under test. I'm not even sure where one would connect an external capacitor ? I suggest you call them again and this time try and find someone who actually understands the product. Best of luck,,, Michael Hopkins KeyTek -----Original Message----- From: Antonio Cinquino [mailto:cinqu...@cae.ca] Sent: Tuesday, December 05, 2000 8:46 AM To: 'emc-p...@ieee.org' Subject: Blocking Cap for 1000-4-4 (EFT) Hello Group, Question with regards to EFT Immunity testing on power lines. We have a post installation setup that allows for only the direct injection EFT method described in IEC-1000-4-4. A figure is given on page 49 (figure 10). We will use a 2kV test level. Anyway, my question concerns the 33nF blocking capacitor. The figure says to use them "if necessary". I'm assuming that depends on if your EFT generator has in-built protection or not. We use the NSG 3025 from Schaffner. Phoned them, and they said to use the caps. Now, should the caps withstand a working voltage of 2kV (peak)? Or should it have a dielectric strength that withstands 2 kV? (I assume that dielectric testing by the manufacturer is done for a very short duration whereas our EFT testing will last for about 1min for each polarity) Are there any other factors to consider in selecting the capacitor, given the type of waveform going through? I've tried a few manufacturers and have had problems up to now finding the right cap. If anyone can suggest a North American Vendor, and even go as far as suggesting the capacitor type then I would really appreciate it. I know it's just a cap :) Maybe I'm over complicating the matter. Anywho looking forward to hearing your responses. Regards Antonio Cinquino CAE Electronics Ltd. Electrical System Designer Phone : (514) 341-2000 (ext. 4303) Fax : (514) 340-5552 Email : cinqu...@cae.ca <mailto:cinqu...@cae.ca> ------------------------------------------- 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
