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Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!genrad!panda!talcott!harvard!seismo!brl-tgr!tgr!jrv@mitre-bedford
From: jrv@mitre-bedford
Newsgroups: net.ham-radio
Subject: MOV transient protectors
Message-ID: <9024@brl-tgr.ARPA>
Date: Thu, 7-Mar-85 01:26:47 EST
Article-I.D.: brl-tgr.9024
Posted: Thu Mar  7 01:26:47 1985
Date-Received: Sun, 10-Mar-85 06:47:44 EST
Sender: news@brl-tgr.ARPA
Lines: 13

I can't see why more than one MOV would be necessary to protect the AC
power (hot to neutral), because I can't see anything that would drive
a transient from hot to ground or ground to neutral.  Big, inductive
loads switching on and off (motors, relays) create transients from hot
to neutral.  Any sources outside the building can only drive
transients from hot to both ground and neutral, because ground and
neutral are connected at the circuit breaker box.  Assuming the
building is wired with grounded outlets, all three wires run in
parallel from the breaker box to the outlet, so even VHF radiation
can't drive a big differential mode signal.  The only source I could
think of for a big signal from ground to something else is a lightning
strike to just one wire - and I wouldn't expect any MOV to handle
that!  - Jim Van Zandt