Cortland, It is quite possible that we are fighting a similar ghost. I imagine that there are an infinite number of strange conditions that can occur on the AC Mains which could cause such a failure. Who knows? For instance, the problem might be a third party product that is becoming popular in labs that commonly purchase our instruments that is creating some kind of strange signal or transient that is causing our power supplies to self-destruct.
Another example: Several years ago we had an instrument as a customer site (in India) that was blowing up the power supply every time they turned the furnace up to its highest power level. We spent two months trying to simulate the condition here in our EMC lab without any luck. Our company even shipped them a replacement instrument which ended up having the same problem. At the point we knew the problem was external. When we pressed our customer for more information we found out that when our service personnel was not on site, they would power our instrument with an AC Power Line Conditioner that turned out was Under-rated for the current our instrument needed. Under full load, this line condition would do something strange which blew up the power supply. Unfortunately we were never able to determine what this condition was. With the many good advice we have received so far and our determination to resolve this I know it is just a matter of time before we figure it out. Thanks again for everyone's help. The Other Brian -----Original Message----- From: CR [mailto:[email protected]] Sent: Thursday, September 17, 2015 11:10 AM To: [email protected] Subject: Re: [PSES] Unexplained High Fallout of Power Supplies On 9/17/2015 9:37 AM, Kunde, Brian wrote: > The issues we are having are with these purchased power supplies blowing up. > And because we pre-test power supplies and our finished products so > extensively and we are not able to cause a power supply failure with the same > damage pattern as we are seeing in the field, we believe that in the real > world our products are seeing some kind of condition that we are not able to > simulate in our EMC Lab. Identifying and understanding such conditions is our > goal at this time. Let me back up a bit... suppose it Is an external event; you will need to know how bad it is and what it looks like in order to track it down and protect against it. Some years ago I was able to resolve a mystery problem because (on a hunch) I'd taken along a 10 Hz-5 MHz loop and was watching a 'scope connected to it. None of the normal GR-1039 tests would have caught it, as the failuresoccurred inside an operating[test] telco Central Office. I was seeing a large magneticfieldtransientcaused by ring-tone current switching affecting customer-premisesmodems temporally placed inside the CO.That problem went away once they were moved down the hall. A problem quite similarto yours occurred later, on remote digital loop equipment cabinets connected to outside plant wiring; protector blocks were failing destructively, evenin the absence of lightning or any known stresses. I was laid off in a downsizing and that employer no longer exists, so I don't know if it was solved, or even if it was pursued after I left, but Isuspect that (again) the observed failures were caused by events we could have foreseen had we thought past the tests required by the standardto which we conformed. *I now suspect **charges induced****i**n a **the extensive outside plant overheard wiring **as **highly charged clouds drifted past.* You have an even larger outside plant. I suspectyour problemis of a like sort, onenot just outside the box; outside the BOOK. Plausible, possible and detectable, if you know what to look for. Cortland Richmond - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
