Hi Joe, IEC60950, clause 1.5.9.2 requires - for the protection of the VDR - "an interrupting means having an adequate breaking capacity shall be connected in series with the VDR"
Best regards Kris Carpentier, From: Joe Randolph [mailto:[email protected]] Sent: dinsdag 31 oktober 2017 3:09 To: [email protected] Subject: [PSES] Regulatory requirements for MOVs placed line-to-ground on AC mains ports? ** WARNING: This mail is from an external source ** Hello All: Aside from surge tolerance during normal type testing, are there any regulatory requirements regarding the placement of MOVs from line to ground on an AC mains input port? I seem to recall that some countries or standards are concerned about potential hazards associated with MOVs developing high leakage current, over time, in response to repeated surge events. I've seen circuits where a GDT was added in series with the MOV, and I believe this had something to do with concerns about MOV leakage current. I've also seen MOVs offered for sale that are packaged in a way that physically couples them to a thermally-activated one-time fuse. This implies a concern with the MOV becoming leaky over time and overheating. While I am familiar with the potential failure mechanism of MOVs developing high leakage current over time, I cannot point to any published safety standard that imposes any construction requirements that attempt to protect against this failure mode. I thought I remembered seeing something on this topic many years ago in a UK standard, but that was a long time ago, prior to harmonization of the IEC 60950 series. Thanks, Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected]<mailto:[email protected]> http://www.randolph-telecom.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 <[email protected]<mailto:[email protected]>> 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)<http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
