[Amps] MOVs

Jim Brown jim at audiosystemsgroup.com
Wed Jan 9 13:59:00 EST 2013

On 1/7/2013 9:50 AM, Vic K2VCO wrote:
> Here in the US I would use a 130V MOV from each hot wire to ground. 
> But clearly that wouldn't work in a place where one side of the 240V 
> line is grounded.

That is NOT a good thing, because the spike raises the instantaneous 
voltage on the green wire. That can (and often does) cause destructive 
failures of interconnected equipment powered from a different outlet.  
The ONLY safe way to use MOVs on branch circuits is between two hot 
conductors, or between hot and neutral.

In nearly all of the world, power uses a neutral conductor that is 
bonded to an "earthed" conductor either at the entrance to the premises 
or in power company wiring.  HOW and WHERE that takes place varies from 
one country/region to another, as do the line to neutral voltage (100, 
120, 240) and frequency (50/60 Hz).  All of this is detailed in a 
tutorial I was hired to write for a pro products company that sells to 
the pro audio and video contracting market.


While some of the thrust of this piece is geared toward large public 
buildings, the fundamental concepts don't change.  This piece also 
addresses the issues that can arise with use of MOVs.

73, Jim K9YC

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