My safety people are telling me that part of Ed. 2 also requires that VDR's line to line ( or line to neutral) have secondary protection. Either a fuse, gas tube, or double insulated cap. They have been with great gusto been pulling out the VDR's or replacing them with fused versions.
>From an EMC aspect, we never know when a VDR (from now on MOV) goes bad. SO.... with respect to line to line (neutral) MOV's only and Ed.2 Do MOV's need a secondary protection? thanks for any comments Regards David Spencer EH&S EMC Engineer Xerox Corp -----Original Message----- From: emc-p...@ieee.org on behalf of Bill Owsley Sent: Wed 12/15/2010 3:57 PM To: EMC-PSTC@LISTSERV.IEEE.ORG; oconne...@tamuracorp.com Subject: RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. In EMC are testing to 2 kV surge. But Brazil deemed our product "telecom" and applied 4 kV. A couple of our products spark and arc impressively and continue running. A couple of others quit, died, castors up, and the smoke got out... (It fun when they do that!) EMC says it has to continue to work. Safety says it only has to fail safely. Engineering says fix it but don't change anything. VDR between line and earth, and between line to line fixes it to 4 kV. But I run right into the safety guy and all these notes, about pluggable, single/double fused, screwed down earths, permanent connect, etc. Bill In the event of a national emergency, click on the following links to provide directions to your duly elected mis-representatives.http://www.usa.gov/Contact/Elected.shtml or... https://writerep.house.gov/writerep/welcome.shtml http://www.senate.gov/general/contact_information/senators_cfm.cfmif really desperate... http://www.usa.gov/Contact/Elected.shtml --- On Wed, 12/15/10, Brian O'Connell <oconne...@tamuracorp.com> wrote: From: Brian O'Connell <oconne...@tamuracorp.com> Subject: RE: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and VDR bridging basic insulation. To: EMC-PSTC@LISTSERV.IEEE.ORG List-Post: emc-pstc@listserv.ieee.org Date: Wednesday, December 15, 2010, 3:33 PM The problem with the VDR being rated for a level 3 surge, which is significantly greater than the typical test V for BI, is that the VDR will typically start conducting long before required test voltage is reached. Di-electric withstand and surge immunity are very different animals. I saw a VDR from line to chassis in a competitor's component P/S - never understood the reason for this construction. Is the VDR rating for 62368 conformity a working voltage or surge rating ? Brian > -----Original Message----- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf > Of Richard > Nute > Sent: Wednesday, December 15, 2010 12:01 PM > To: JIM WIESE > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] IEC 60950-1 Ed. 2 Class A Pluggable equipment and > VDR bridging basic insulation. > > > Hi Jim: > > Thanks for your remarks. > > You CAN remove the VDR during hi-pot testing. > This is specified in 5.2.2: > > "To avoid damage to components or insulation > that are not involved in the test, > disconnection of integrated circuits or the > like and the use of equipotential bonding are > permitted." > > This is for the "type" test, not the "routine" > test. Nevertheless, your point is well taken. > > Also note that 5.2.1 specifies: > > "The electric strength of the SOLID INSULATION > used in the equipment shall be adequate." > > So, the hi-pot test only applies to solid > insulation. > > The other option is to specify the VDR at a higher > voltage than the hi-pot test voltage. > > Regarding VDRs, I don't know why any equipment > would need a VDR between mains and earth. The > requirements for clearance, creepage, and solid > insulations require an electric strength at least > as great as the expected transient overvoltage, > regardless whether a VDR is between mains and > earth or not. So, the VDR does not protect > anything against any voltage up to the required > electric strength of the equipment. > > The VDR *may* be useful to protect against > transient voltages exceeding the required electric > strength.n which case it will pass the hi-pot > test. > > In the new IEC 62368, the requirement is that any > VDR between mains and earth shall be rated greater > than the required electric strength. > > > Best wishes for the Christmas season, > 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://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 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 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>
