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Re: [Amps] MOVs

To: amps@contesting.com
Subject: Re: [Amps] MOVs
From: Vic Rosenthal K2VCO <k2vco.vic@gmail.com>
Date: Thu, 23 Jan 2014 07:48:02 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
I put a 320V MOV across the primary of my plate transformer (no connection to ground) to soak up differential mode spikes, on the grounds that this might help protect the diodes. I have no idea if it's necessary or helpful, but I can't see how it could hurt. Motors like air conditioner compressors can produce such spikes, and I have seen cases in which computers rebooted themselves every time a compressor went off.

On 1/22/2014 10:45 PM, Jim Brown wrote:
Because MOV's conduct surge currents onto ground, and the IR (and IZ)
drop raises the potential of the chassis. When the "protected" equipment
has a low voltage connection to other equipment powered and/or grounded
at another point, the difference between one chassis and the other often
fries the interface circuitry.

I've seen many well-documented examples of this with audio systems, and
with computers connected by wired Ethernet, no radios anywhere around.
The sharp guys in pro audio stopped using MOVs at least 20 years ago.

73, Jim K9YC

On 1/22/2014 10:11 PM, Jim W7RY wrote:
Why?

On 1/22/2014 9:59 PM, Jim Brown wrote:
On 1/22/2014 8:40 PM, Gary "Joe" Mayfield wrote:
What are folks thoughts
about MOVs on the primary side of the transformer?

Bad idea. ANY MOV on branch circuits is a bad idea.

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/

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