Brian,
950 says that a VDR in a Primary circuit SHALL comply with 61051-1 and one of the requirements is the list of preferred voltages. I know at least 1 safety lab that reads the standard as I do. I don’t know what arguments some other labs have to ignore that list. And now we talk about varistors in the primary, the next item is how we protect that varistor according to 950, clause 1.5.9.2. Some safety labs think it can be done with a 2A fuse in series, others are of the opinion that a thermal fuse is the only suitable solution. Personally, the 2nd solution is the only one that makes sense, but most wall mount PSU in the field are not equipped with a thermal fuse. Best regards, Kris Carpentier From: Brian O'Connell [mailto:[email protected]] Sent: zaterdag 5 juni 2010 1:18 To: Carpentier Kristiaan; [email protected] Subject: RE: VDR recommendations Hello Kris, Is this voltage 'list' normative? If so, then I may not understand what I am looking at, because I have seen a max cont V ratings of 300V on several VDE certs. Bad things would probably happen if I have to use a VDR rated at 420V. thanks much, Brian From: Carpentier Kristiaan [mailto:[email protected]] Sent: Friday, June 04, 2010 4:05 PM To: Brian O'Connell; [email protected] Subject: RE: VDR recommendations Hi Brian, Annex Q (normative) is referring to IEC 61051-2 and the requirement in b) The max. continuous voltage (2.1.2 of IEC 61051-2) is selected from the list of preferred voltages and shall be at least 120% of the RATED voltage or the upper voltage of the RATED voltage range. This list is 60 130 250 275 420 460 680 1000V rms. So if the RATED voltage is 240V, the minimum varistor type shall be 420V Some Safety labs understand this requirement, some don’t. Best regards, Kris Carpentier From: [email protected] [mailto:[email protected]] On Behalf Of Brian O'Connell Sent: zaterdag 5 juni 2010 0:09 To: [email protected] Subject: VDR recommendations Looking for VDRs that are rated for 288V continuous (see annex Q of 60950-1). Lots of stuff rated 275V and 300V, but cannot find anything in between. Why ?!?! - because I have done some surge tests using 300V components on a custom unit and was not satisfied with results - nothing terrible, just no warm feeling from a test completed with good margin. Currently use Epcos, Panasonic, and UCC. thanks, 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
