Hi Ken:
For safety purposes (protection against electric shock), insulation between the mains and the human body must not only withstand the mains voltage, but also must withstand transient voltages on the mains. These transients are normal and are generated by normal load switching and by lightning. The hi-pot test verifies that the insulation, both solid and air (clearance), will withstand the transient voltages and thereby provide protection against electric shock (from the mains). Your 28 volts dc is below the electric shock threshold for dc, which is taken as 60 volts in some safety standards and lower in other safety standards. So, from a safety point of view, we don't care whether the insulation will withstand transient voltages, e.g., brush noise. The insulation can fail, but no electric shock is likely. In the safety field, we would say that the 28-volt insulation is functional, and is not a safeguard. For safety, no hi-pot testing is required. You may want to do the hi-pot test for functional purposes. And, you can use any caps you desire. The traditional hi-pot test voltage for mains circuits is twice rated plus 1000 rms. For a 28-volt circuit, you can choose any test voltage that, to you, seems reasonable. Good luck! Rich From: Ken Javor <ken.ja...@emccompliance.com> Sent: Monday, August 13, 2018 1:22 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] X & Y Cap rating due to hipot test More on this topic. The basic question is, "what is the prupose of hipot testing?" The context is a 28 Vdc brush motor that needs some caps to filter brush noise. Looking at some quell/eeseal chip caps on an insertable template that fits in the connector shell. I contend that could be inserted after hipot testing, so that the insert caps don't have to be rated to 1000 volts. The 1000 volt rating limits the selection of available caps. As I understand it, hipot testing ensures safety by verifying sufficient separation between different conductors. Why would it be necessary to apply a hipot test to a connector insert? Thank you, Ken Javor Phone: (256) 650-5261 _____ From: Ken Javor <ken.ja...@emccompliance.com <mailto:ken.ja...@emccompliance.com> > Date: Fri, 10 Aug 2018 15:13:23 -0500 To: "doug...@gmail.com <mailto:doug...@gmail.com> " <doug...@gmail.com <mailto:doug...@gmail.com> >, <EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> > Conversation: [PSES] X & Y Cap rating due to hipot test Subject: Re: [PSES] X & Y Cap rating due to hipot test Thank you, Ken Javor Phone: (256) 650-5261 _____ From: Doug Powell <doug...@gmail.com <mailto:doug...@gmail.com> > Reply-To: Doug Powell <doug...@gmail.com <mailto:doug...@gmail.com> > Date: Fri, 10 Aug 2018 13:41:40 -0600 To: <EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: Re: [PSES] X & Y Cap rating due to hipot test Ken, Yes and No, the line to line "X" caps will not see hipot potentials since you should tie lines and neutral together during the test. Line to earth "Y" caps will see the entire voltage during the test. This assumes of course you have manually closed any circuit breakers, contractors or switches that may otherwise isolate the equipment internals. All the best, Doug -- Douglas E Powell doug...@gmail.com <mailto:doug...@gmail.com> https://www.linkedin.com/in/dougp01 Sent from my Android on the Verizon 4G LTE Network From: ken.ja...@emccompliance.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>
