Re: [PSES] OSM decision

[Douglas Smith]

Hi Rich and the group, Even DC power internal busses in equipment are likely to have 1000 Volt transients if hot plug of power supplies and/or loads are allowed. Outside transients are not necessary to have this happen. I have personally observed these EFT events. The effect on the power supply control circuits (sources and loads) is a lot like ESD causing over voltage/over current shutdowns and potentially other problems. The protection circuits should have limited frequency response to ward off problems of false trips. Their response time should be as long as can be tolerated but no faster than one microsecond. Doug University of Oxford Tutor Department for Continuing Education Oxford, Oxfordshire, United Kingdom -------------------------------------------------------------- ___ _ Doug Smith \ / ) P.O. Box 60941 ========= Boulder City, NV 89006-0941 _ / \ / \ _ TEL/FAX: 702-570-6108/570-6013 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: d...@dsmith.org \ _ / ] \ _ / Web: http://www.dsmith.org -------------------------------------------------------------- On 1/26/15 6:11 PM, Richard Nute wrote:   Hi Brian:      (An equipment d.c. bus is not likely to have high-voltage transients.)   AC mains input to this equipment, so must assume the box will see at least 2500V   The transient overvoltage is not likely to appear on the d.c.  Conduct a test by applying the 1.2x50 2500-volts peak pulse to the a.c. mains.  If you don’t have the pulse generator, use a 2500 volts peak hi-pot tester.  This will prove whether you need the MOV.  I’ll bet you can take the MOV out.     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> - ---------------------------------------------------------------- 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>