DB>There was a German study published partly in Computer Shopper, Jim.
DB>I could look it up, but hopefully this will be clear enough...
DB>They started to look at fires in buildings which had large numbers
DB>of computer systems in simultaneous operation.  They noticed some
DB>increase in electrical fires in main switch boxes and associated
DB>transformers.
DB>What they found was that there was a harmonic reaction, where two
DB>or more PFC power supplies would get in sync, trying to modify
DB>what each perceived as distortion in the incoming AC sin wave as
DB>it was delivered to the computer load.
DB>Within milliseconds every PFC in the building would pick up on a
DB>ripple reflected back into the local grid, and the whole setup
DB>then avalanches into a feedback loop forcing the current/voltage
DB>peaks to blow the mains in the building.
 Since the first stage of a switching power supply is a simple
rectfier and capacitor filter (basically), I don't see how a high
level, high frequency "signal" could make it onto the power line
to cause these type of symptoms. If it did, a simple filter system
should be able to rectify the problem.
 This is really off topic; so, if you want to continue this, we'll
have to take it to another echo.
 Later.
 Robert
 * SLMR 2.1a * This is too easy! I must be doing it wrong!
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