[Amps] MOVs

[Carl]

Inductive industrial equipment use big MOV's for spike suppression on single 
and 3 phase lines of many voltages.

I use a pair of large Littlefuse MOV's as a whole house limiter and right at 
the main panel.
Lines that are used with electronics when on generator power are also 
treated with MOV's and .01/2KV buffer rated disc caps.

The oscilloscope traces look very good now compared to just the junk coming 
in from the utiity line. The generator crud was expected and limited decades 
ago.

Carl
KM1H

----- Original Message ----- 
From: "Vic Rosenthal K2VCO" <k2vco.vic at gmail.com>
To: <amps at contesting.com>
Sent: Thursday, January 23, 2014 10:48 AM
Subject: Re: [Amps] MOVs


>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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