For general I.T., there is no requirement for a component power supply output to maintain SELV levels during a surge. Typically, if a power supply propagates the surge to an output, the power supply will fail. The power supply should, for most TNV installations, fail without being a fire or shock hazard.
For CO environments, the power supply must be meet the surge tests of UL60950-1 section 6.2, which is NOT the same as the 61000-4-4,5 stuff. And if you need to meet CO, a secondary surge suppression device should conform to IEC61643-21. Where a surge suppressor is required for protection from shock, the surge device must be connected directly to the P.E. terminal. Brian -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Bill Owsley Sent: Thursday, September 09, 2010 9:25 AM To: [email protected]; BrianKunde Subject: RE: Surge Pulse After Line Filter Several places, output of surge generator, input to EUT, output of EUT, assuming EUT is a power supply (usually with filters built in). We have seen higher than expected voltages on the output, but not yet higher than the surge. The higher than expected on the power supply output means the SELV circuits are not staying SELV. I am not the Safety engineer, just the EMC geek. It sounds like in your case, you are measuring in the middle of the EUT, between filter and power supply. A great place for diagnostics if you are getting a fail. And that filter seems very interesting indeed. Bill --- On Thu, 9/9/10, Kunde, Brian <[email protected]> wrote: From: Kunde, Brian <[email protected]> Subject: RE: Surge Pulse After Line Filter To: [email protected] List-Post: [email protected] Date: Thursday, September 9, 2010, 11:46 AM Bill, Where are you monitoring the surge voltage? At the output of the surge generator? In our case, the generator output looks fine, but when we look at the surge pulse at the input to our power supply (after our line filter) the surge pulse is much larger. Case in point, I am currently working on piece of equipment that has a 500 watt 24Vdc power supply connected after a 60 amp line filter. The 2KV Line to PE surge pulse is 3500 voltage at the power supply. The Other 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]>
