[Amps] MOVs

Vic Rosenthal K2VCO k2vco.vic at gmail.com
Thu Jan 23 10:48:02 EST 2014

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.

Vic, K2VCO
Fresno CA

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