Re: [PSES] Unexplained High Fallout of Power Supplies
Brian, How is the furnace shut off? If you are using a contactor between the main line filter and the furnace, a phase line might open when it is carrying high current. The inductance of the line filter will try to keep this current flowing, generating a very-high kickback spike at the *output* of the line filter. Or, since the contacts in the contactor are unlikely to open/close at exactly the same time, a common-mode choke in the line filter can act as a transformer putting noise on the open phase(s) if only 1 or 2 phases are connected to the load. Some years ago, Bill Kimmel and Daryl Gerke wrote about a case where a 3-phase product had a contactor between a line filter and the load, which generated horrendous Conducted Emissions noise every time the contactor opened or closed, because of this transformer action. The solution was to replace the common-mode choke with 3 separate chokes, one for each phase line. John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, Master EMC Design Eng, SM IEEE (retired) Lexington, KY http://www.dbicorporation.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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Unexplained High Fallout of Power Supplies
I would look at the various overvoltage protection circuits. When OVP operates, it may protect the immediate circuits from damage. But, when an OVP operates, the energy stored in the supply circuit inductances and capacitances has to be dissipated somewhere else. The energy can go anywhere on the supply network. "An SPD puts a momentary very low impedance to earth on the distribution system. Such a tactic assumes transient overvoltages can be eliminated by connecting them to earth. The sudden change in current causes a change in the field of an inductor which causes a transient voltage across the inductor."* *Diverting Surges to Ground: Expectations versus Reality, François D. Martzloff, Proceedings, Open Forum on Surge Protection Application, NISTIR-4654, August 1991, National Institute of Standards and Technology, Gaithersburg, MD Joe Randolph presented a paper at the 2013 Symposium, and re-published this year in In Compliance magazine. His hypothesis is that OVP operation created the failures that he could not otherwise explain. He had data which supported his hypothesis. Best regards, 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Unexplained High Fallout of Power Supplies
" provoked into spontaneous energetic disassembly." -> Will use that phrase on next TRF/report. The component with least margin tends to the main switch transitor(s). Mostly because of peak voltages at end of each cycle. Resonant-mode converters have less Vpk but more periodic RMS stressors. But as energy is easily controlled for each individual cycle, response to an external disturbance typically results in rapid shutdown of the gate drive. The circuit node that tends to have the most circulating energy is junction of PFC choke/diode/switch; and once the choke saturates, bad things start to happen. Typical PFC controllers run in transition mode or continuous-current mode, but the more recent fixed off-time controllers allows hi-current control, and can handle boost-choke saturation. Power transistors have greatly improved last ten years. Idss leakage spread has decreased an order of magnitude and breakdown V has decreased 50%. So if the power supply is not using recent stuff, you have no significant margin. Legacy stuff - cheap but has some evil failure modes buried in most power supply designs. New stuff - more cost but less boom. Brian -Original Message- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Tuesday, September 22, 2015 11:10 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Unexplained High Fallout of Power Supplies In message <64D32EE8B9CBDD44963ACB076A5F6ABB02717445@Mailbox-Tech.lecotech.local>, dated Tue, 22 Sep 2015, "Kunde, Brian" writes: >I'm guessing that under some conditions, there could be some kind of >interaction between the rf filter and the power supply which maybe >causing our high fallout. Can you propose a test setup where we might >be able to simulate such conditions? I'm guessing the same, just from your report of the damage, but as I said about 50 k posts ago, I failed to understand the stability issues with PFC circuits. I just know that they can be provoked into spontaneous energetic disassembly. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk When I turn my back on the sun, it's to look for a rainbow John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Unexplained High Fallout of Power Supplies
In message <64D32EE8B9CBDD44963ACB076A5F6ABB02717445@Mailbox-Tech.lecotech.local>, dated Tue, 22 Sep 2015, "Kunde, Brian" writes: I'm guessing that under some conditions, there could be some kind of interaction between the rf filter and the power supply which maybe causing our high fallout. Can you propose a test setup where we might be able to simulate such conditions? I'm guessing the same, just from your report of the damage, but as I said about 50 k posts ago, I failed to understand the stability issues with PFC circuits. I just know that they can be provoked into spontaneous energetic disassembly. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk When I turn my back on the sun, it's to look for a rainbow John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Unexplained High Fallout of Power Supplies
A failure in PFC section most onerous when a surge finds its way to the choke/diode/switch node. Any significant voltage 'reflected' into the gate of the PFC transistor will typically cause power supply to puke it guts. Looks like data that would indicate a root-cause failure remains elusive - seems to be a need something non-intrusive that is self-powered and can get kicked yet stand back up for more abuse (please sir, may I have another...). During 2013, tried several commercial loggers over a six-month period and most did not survive the end-use environment . The two that lived through their ordeals had insufficient bandwidth, or had insufficient dynamic range, or had immunity problems, or used too much power, etc. So ignored the 'Not Invented Here' accusations and rolled own design. Second fielded version worked ok and management wanted to turn it into a standard product - but were able to convince otherwise by explaining the level of customer support required for various windoze computers that would be used to suck in the log files; and that marketing said could sell no more than 3 units per month of a specialty product (mostly used to monitor power converters, transformers, and reactors used on PV arrays). My latest incarnation of The One True Monitor Box looks at seven thermocouple channels, four Vdc (200-1500V) channels, three RMS (230-480V), two light sensor channels, and seven current channels; an array of four peak V (envelope detector) channels that can be paralleled with the voltage channels(mostly to detect when to go to hi-speed sample rate and use different data structure); and four comparator channels (hi-rate event triggers). The support from the good engineers at LT, ADI, Micrel, and TI was instrumental (pun intended) in this design. Have recently started using these loggers to monitor long-term Type Tests where there is a risk that the test conditions might kill my standard lab setup (Agilent34970/computer combo - $100 vs $3000 USD of equipment). The (im)moral of the story is that compliance engineering thrives where reliable *end-use* empirical product data is available. 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Unexplained High Fallout of Power Supplies
-- Original Message -- From: "Kunde, Brian" Date: Mon, 21 Sep 2015 20:13:33 + 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Unexplained High Fallout of Power Supplies
John, Yes, the large rf filter is still in the circuit but only supplying less than few amps of current to the 24Vdc power supply. The High Current Furnace branch would be an open circuit. The worst case would be in a 50 amp (rated) instrument where we have a 65 amp RF Line filter driving a 500 watt 24Vdc power supply (about 1 amp at 50% load), when the furnace is not running. The furnace only runs about 30-60 seconds at a time per analysis. So it is off most of the time. I'm guessing that under some conditions, there could be some kind of interaction between the rf filter and the power supply which maybe causing our high fallout. Can you propose a test setup where we might be able to simulate such conditions? Thanks for the input. The Other Brian -Original Message- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Monday, September 21, 2015 4:40 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Unexplained High Fallout of Power Supplies In message <64D32EE8B9CBDD44963ACB076A5F6ABB02717398@Mailbox-Tech.lecotech.local>, dated Mon, 21 Sep 2015, "Kunde, Brian" writes: >The word we get from the field is that these 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. When you say 'it's not running', I understand that the furnace current isn't flowing, but is the filter connected to the mains supply? If so, that is possibly a more hazardous condition, because a filter with open-circuit output can produce high voltages. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk When I turn my back on the sun, it's to look for a rainbow John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
[PSES] OT - Reference for testing laboratory for IEC 61156-1?
Hi All, This is not specifically EMC/Safety related, but many in this group are either test labs or work with various test labs and may be able to help. I was hoping someone could provide a recommendation towards a commercially available 3rd party test lab that performs IEC 61156-1 evaluations, preferably in North America. This is a specification related to multi-pair cable characteristics. Best Regards, Scott Drysdale http://ca.linkedin.com/in/scottdrysdale OOO - Own Opinions Only - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
