Possibly because standards provide an RMS level for AC dielectric and that never seems to be as high as the 'equivalent' DC dielectric test. Since dielectric strength test checks for sufficient clearances, the DC test would be tougher on solid insulation. Many standards say to us 1.41xAC for a DC test, presumably since any arc would occur at the peak of the AC test voltage.
There is also some confusion about whether a leakage current limit should be imposed during dielectric tests. It depends on what you think you're checking during routine hi-pot. If creepage distances are compliant and you control what solid insulation is used as a critical component, I think you need only look for breakdown, not leakage. _____________________________________________________________________________________ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: Brian Oconnell <oconne...@tamuracorp.com> To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 11/30/2011 09:47 AM Subject: [PSES] UL assessment of plastics - DC vs AC Received a newsletter from UL. Said that they are looking into updating standards to account for DC di-electric withstand vs AC. I can understand that the physics of dc arcing and tracking could be different from ac, but why would the dc di-electric withstand be more onerous than ac? Perhaps they are mixing IR and di-electric withstand, which cannot be considered a similar test. Brian - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com> ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
