[TowerTalk] MOVs in Stackmatch

[Roger (K8RI)]

Rick Stealey wrote:
>
>  Is there any 
>   
>> way with minimal equipment to see if an MOV is still good? The relay 
>> coils all appear OK, so I guess they did their job.
>>     
>
> Pete,
> If you put dc on them, with a series resistor to limit the current to about 1 ma
> you will see the breakdown voltage.  
> I have done this many times, and used MOVs on rotor control lines, and tested a
>  Polyphaser rotor protector which is just MOVs across the lines and know this will work.
> If you find zero volts or no current flowing you know you have a blown MOV.
> You can get huge rated MOVs from Mouser for 30-50 cents each.
>   

Depends on what you mean by huge.  I have some 50,000 Joule capacity 
MOVs and they are big.  Used across the input  to a few hundred KW at  
440 VAC.  When one of those lets go you don't really want to be close 
unless wearing a face shield and really good hearing protection. I've 
seen them leave a pair of #6 wires standing straight out from where the 
MOV had been and  they are louder than a 12 ga fired in a small space.

73

Roger (K8RI)
> Here is a sample of an approximately 30 volt MOV.  Mouser part #576-V39Z


> A20P.  
> This will get you to the right page on the Mouser site.
>
> Rick  K2XT
>
>   
>
>
>
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