On 9/15/2015 4:53 PM, Kunde, Brian wrote:
we have not been able to find the reason for the fallout. The power supplies have all shown arc damage to the AC front end, signs of arcing and traces burned or vaporized, blown fuses, and shorted FETs and/or Rectifiers. These failures have occurred on several different locations, on different power supply models, different manufactures and on different instruments. Some instruments have been in service for years; some for only a few weeks before they fail. Some instruments even have surge suppression modules installed and though the power supplies fail the surge modules tested out fine. The failures did not occur during any known lightning storm or any other known transient.
Brian,
The circumstances you describe -- arcing with no external transient seen -- point to an on-board occurrence, not an external one. I'd suspect (in no particular order and on little information -- heh) ) PWB material with insufficient dielectric withstand, and/or oscillation in a power FET due to its characteristics (or another device's) having changed enough to make the control loop unstable. You might have an oscillator the controller can't even detect.
I'm on LinkedIn if you need help, eh? Cortland Richmond - ---------------------------------------------------------------- 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]>
