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.
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