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] 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 ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Bill Owsley Sent: Thursday, September 09, 2010 11:25 AM To: [email protected]; Brian O'Connell Subject: RE: Surge Pulse After Line Filter What is the setup, the equipment arrangement, etc. for the surge test? I monitor the surge voltage and have not seen the common occurrence of much higher voltages, so I'm wondering what am I missing. I'm not Brian, either one of them... Bill --- On Tue, 9/7/10, Brian O'Connell <[email protected]> wrote: From: Brian O'Connell <[email protected]> Subject: RE: Surge Pulse After Line Filter To: [email protected] List-Post: [email protected] Date: Tuesday, September 7, 2010, 5:09 PM Only one of my esteemed power supply competitors has replied - most dissapointing. Another important principle for 'surge' ratings for component power supplies is the energy. The I^2T is what sends the power supply to the dark side. A customer from the Great State of Australia was killing my children. Cannot be, said I, as all knew the unit was rated level 3 and tested higher. But I must see, said I, as I was still in disbelief. Set this before your beady green eyes, the customer said, and I did. Behold, the addition of evil caps in front of the sacred input filter. Sacrilege said I. I bade them a non-fond farewell. The intended end-use of X and Y caps is NOT surge suppression. They are rated for some big hits, but they are NOT intended to function as a VDR within the meaning of IEC60950-1 annex Q. These caps are considered part of the 'line' filter. But it should be noted that for some resultant surge waveforms, an input-filter cap will appear as a very low Z for a short period before the VDR starts to conduct. There can be an interaction between a front-end pi filter and the resultant shape of the waveform that is propagated into the power supply during a surge event. This is why I re-test surge immunity if the designer changes LC values. Pat, from SL Power, noted the common combo of VDRs and gas tubes. The only problem with gas tubes is turn-on time. But once the gas ionizes, the conduction is on hard, regardless of the waveform and adjacent L. But the more important issue - who among us shall be considered the original 'Brian' ? Brian -----Original Message----- From: [email protected] [mailto: ---------------------------------------------------------------- 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]>
