Forwarded for Jim Bacher -------- Original Message -------- Subject: Re:Oh those maddening MOV's!! List-Post: [email protected] Date: Mon, 2 Apr 2001 16:34:21 -0500 From: [email protected] (Jim Bacher) To: "McCoy; Paul" <[email protected]>,"'[email protected]'" <[email protected]>
Popcorn and Smoke, this is not an answer to your question, just an interesting failure of MOV's that relates to your question. About five years ago, first thing in the morning, as everybody came into the wing I was in, they would turn on the electrical strips that their PC's were plugged into. And most of the strips contained MOV's. A few minutes later there would be a POP and smoke would pour out (flames in a few cases) of the electrical strip. In the matter of a few minutes we lost over 25 electrical strips. It was the same morning and the same time they were scrolling messages on who had just bought our company. It seems that one of our cubes had been miss wired. It seems that line and neutral had been reversed. As a result the fuse / circuit breaker of the electrical strip was in the neutral leg rather than the line side. As MOV's do once in a while, the MOV that was line to ground failed as a short circuit (the MOV without the protection). The MOV happened to be wedged against the metal of the strip so it could dissipate a little more power than normal. Once it shorted to ground some even more interesting things happened. Our wing is run on three phases. It turns out that the ground was not installed correctly and a main ground wire to the wing had failed. So when the MOV shorted, it basically lifted the ground of our wing to phase A's potential. All of the MOV's on phase B and C then had twice their nominal voltage applied and without having the extra heat sinking that the first MOV had, they were popping like popcorn. None of the computers were damaged, only the electrical strips were damaged. Jim Jim Bacher, Senior Engineer Paxar - Monarch e-mail: [email protected] voice: 1-937-865-2020 fax: 1-937-865-2048 ____________________Reply Separator____________________ Subject: Oh those maddening MOV's!! Author: "McCoy; Paul" <[email protected]> List-Post: [email protected] Date: 4/2/01 3:30 PM Group, I know in conversations and threads past there has been discussion on the use of MOV's and gas arrestors for the main power input. Specifically at which times and under what conditions an MOV can be placed between LINE and PE. Could some one please tell me what standard (standards?) these requirements come from? Thank you, Paul McCoy ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
