Re Richard Nute's "All of the products I have seen have two Y capacitors, one from L to E, and one from N to E. "
Sorry for the delay in the following comment: I've been on Holiday with no email. I have now checked the 13 mains-powered devices for which I have definite knowledge of their Y cap. disposition. They are all commercially-produced products that are commonplace in domestic or office locations worldwide. Of the 13, 4 have only a SINGLE Class Y capacitor. 4/13 is 30% I think that this represents a trend, since now SMPS are so nearly universal and these give the opportunity - some might say the necessity - to be quite subtle in the circuit design around the Y capacitor(s). Richard Richard Marshall Laboratories, 30 Ox Lane, Harpenden, Herts., AL5 4HE, UK +44 (0)1582 460815 <http://www.design-emc.co.uk> www.design-emc.co.uk Member of the EMC Industry Association From: Richard Nute [mailto:ri...@ieee.org] Sent: 04 April 2016 18:29 To: 'Richard Marshall' <richard.marshal...@btinternet.com>; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] Commom mode current vs. differential mode current and LISN Hi Richard: The usual class Y value of 4,700pF presents an impedance of only 1.13 ohms at 30MHz, so it provides a very substantial unbalance to create CM from a neighbour's DM All of the products I have seen have two Y capacitors, one from L to E, and one from N to E. With these two capacitors, there should be no significant unbalance caused by the Y capacitors. Best regards, Rich - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> 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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
