In this case, while the caps are across the ac line just like an X-cap, the device is test equipment which only monitors the potential across the ac input during EMI testing in an EMI test facility. I had suspected that the difference between a cap rated for ac mains usage and one that wasn¹t was surge-type requirements, which don't seem applicable in this application, but I wanted to hear from the forum on this subject.
And the cap value is around 2500 pF, made up of two 5000 pF caps in series for safety reasons. Thank you, Ken Javor Phone: (256) 650-5261 From: Derek Walton <[email protected]> Date: Fri, 31 Aug 2012 22:06:23 -0400 (EDT) To: <[email protected]>, <[email protected]> Subject: Re: Capacitor rating for mains usage HI Ken, you don't say how small and it's relative you know :-) Any cap I suggest for across the line use I strongly recommend it has an X rating, a Y rating if it goes between power and earth. Is this what you were meaning? Cheers, Derek. -----Original Message----- From: Ken Javor <[email protected]> To: [email protected] <[email protected]> Sent: Fri, Aug 31, 2012 5:58 pm Subject: Capacitor rating for mains usage Forum members, Am trying to spec out some small value capacitors to be placed across unrectified mains potentials. These caps are rated at dc potentials way beyond the peak of the ac bus potential, but they carry no ac rating. What are the issues here? The cap should not breakdown at ac mains potential, so what information does an ac rating provide? Is it related to surge potentials that can appear on ac mains? Thank you and happy Labor Day to those members on the west side of the Pond. Ken Javor Phone: (256) 650-5261 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
