The big deal here is the issue of the energy the varistor must dissipate, which can cause catastrophic failure of the varistor, often resulting in a fire.
I have seen this problem, in the lab after hammering a varistor with successive 6000V surge impulses once per minute. In the lifetime of a product connected to residential branch circuit it's uncertain whether it would ever fail. A pound of prevention supposedly being worth an ounce of cure? _______________________________________________________________________________ Ralph McDiarmid | Schneider Electric | Solar Business | CANADA | Regulatory Compliance Engineering From: Richard Nute <ri...@ieee.org> To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 05/12/2012 05:33 PM Subject: Re: [PSES] Hipot with in-circuit voltage limiting devices IEC 61010-1 3rd Ed. Hi Mick: The "problem" is the one originally described. The 2nd Edition of IEC 62368-1 is the result of an ad hoc group that studied the various varistor components to arrive at a set of requirements that would allow the varistor (and its derivations) to perform the intended "clamping" yet not incur a safety issue. The big deal here is the issue of the energy the varistor must dissipate, which can cause catastrophic failure of the varistor, often resulting in a fire. The ad hoc group concentrated on requirements that would prevent device failure. IEC 62368-1 2nd references IEC 61051 for most requirements. I'm sure the varistor requirements will be again reviewed at the upcoming TC108 meeting in June in Northbrook, Illinois, U.S.A. If you or anyone on this list would like to review and comment on the 2nd Edition requirements, send me an e-mail and I'll send you the draft 2nd Edition along with a comment form, and who to send it to. Best regards, Rich > -----Original Message----- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf > Of Michael Maytum > Sent: Saturday, May 12, 2012 12:01 AM > To: EMC-PSTC@LISTSERV.IEEE.ORG > Cc: Michael Maytum > Subject: Re: [PSES] Hipot with in-circuit voltage limiting > devices IEC 61010-1 3rd Ed. > > > Richard, > To be clear, what "problem" and "subject correctly" are > you referring to? > The IEC 61010-1 3rd Ed problem is specifying a test > voltage of 0.9xclamping voltage. From memory Edition 1 of > IEC 62368-1 never specified a test voltage of this level. Yes > IEC 62368-1 had a twice AC mains safety test, which links > with the twice AC mains test level of IEC 61010-1 3rd Ed. > If IEC 62368-1 doesn't have a test level of 0.9xclamping > voltage, then, yes, it doesn't have that problem. > What is the "subject correctly" you are referring to; > Varistors, safety testing or hipot testing? > > Best Regards > Mick > > > > > Would you like to check the latest draft of IEC 62368-1 to > see if it > > treats the subject correctly? > With respect to this problem, yes, IEC 62368-1 treats > the subject "correctly." > > > Best regards, > Richard Nute > > - > ---------------------------------------------------------------- > 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://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 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://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://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 <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>
