---------- Original Message ---------- From: "Kunde, Brian" <brian_ku...@lecotc.com> Date: Mon, 21 Sep 2015 20:13:33 +0000
Hello Brian, > test to IEC 61000-4-11 I think the problem is line surges external to your units, and you are on the right track when you suspect that all the test equipment is very current-limited, yet the collection systems in your customers' applications are not. Even surge testers have limits, unless the stack is as tall as you are. > power supplies are failing while the instruments are in Stand-by mode > (running but not during an analysis), meaning, > the high current filter is not running at the time of the failures. I've only had so much time to follow this very interesting topic. To be sure it's external circumstances, I'd tie a signal of some sort from the high-current furnace into your line analyzer (or feed both that and an external trigger from the analyzer into a storage scope). If a failure or line surge corresponds to the furnace coming on, then you look inside your unit. Otherwise, Occam's razor is cutting towards line surges from the facility. > failure in our Apps Lab a few nights ago in one of the same units that failed > a few weeks ago. We installed a Surge Suppressor in > an adjacent instrument which did not fail. Our AC Line Analyzer showed a > transient pulse which was clipped off (probably by the > surge suppressor) at 600 volts with a duration of 14us. Did you get waveshape capture? If so, and the peak is quite flat, then it's for sure the TVS in the adjacent device clamped the surge. 14 uSec. is longer than any of the waveforms provided by standard testers. > power supply blew its fuses (one on each side of the line) plus opened an > upstream 15 amp circuit breaker. ... it did not blow > its guts out like previous failures. This one just opened the fuses. We > replaced the fuses and the power supply was functional. I'd say you need some TVS devices... how widely spread, geographically, have been the failures? Transients (often from power line capacitor switching) akin to what was measured in your Lab are more widespread than reported. > Surge Immunity tests on this same instrument with the same surge suppressor > according to IEC 61000-4-5 up to 6KV without > damage. So something is different from this test setup verses the real > world. Check the surge generator; I'll bet its current limit is tightly tied to 8/20 usec waveforms. Grids are not. Still, I'm a bit troubled by the sudden uptick in failures, including in units (correct assumption?) that have been installed and running for a year or more.... Colorado 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 <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
