[Amps] MOVs

[Carl]

----- Original Message ----- 
From: "Roger (K8RI)" <k8ri at rogerhalstead.com>
To: <amps at contesting.com>
Sent: Friday, January 24, 2014 12:14 PM
Subject: Re: [Amps] MOVs


> On 1/24/2014 1:37 AM, Jim Brown wrote:
>> On 1/23/2014 10:02 AM, Carl wrote:
>>> Inductive industrial equipment use big MOV's for spike suppression on
>>> single and 3 phase lines of many voltages.
>>
>> Again, the problem comes with interconnected equipment when the MOV
>> dumps the spike onto ground. Won't repeat previous email. :)
>>
>
> We had some 50,000 Joule MOVs "across" a pair of back to back 1200 amp 
> SCRs.  The "chip in those SCRs was no chip. It was a round slice of 
> Silicon about 1.5 inches in diameter.  The gate was easily seen.  When one 
> of those MOVs failed, it was a spectacular ball of fire and Loud. The MOV 
> were shaped like a trapazoid about 3/4 of an inch thick on a 1/8th inch 
> Aluminum plate.  The MOV would vaporize.  There were no particles flying 
> around.  The wire connections which were either #6 or #8 would be pointing 
> straight out as if they had been pulled...hard! The only thing left was 
> that Al back plate.
>
> I never saw a pair of SCRs survive, so I'm not sure what good they did.
>
> >> I use a pair of large Littlefuse MOV's as a whole house limiter and
> >> right at the main panel.
> >
> > That's an excellent application.
> >
> >> Lines that are used with electronics when on generator power are also
> >> treated with MOV's and .01/2KV buffer rated disc caps.
>
> They would be far more expensive, but wouldn't back to back zener diodes , 
> or strings of heavily rated zeners be more effective?
>
> I have a bunch of stud mounted zeners in the junk box and it seems like 
> that'd be a good place for them.
>
> 73
>
> Roger (K8RI)


Zeners on AC ??
Those Littlefuse V251BA60 MOV's list at $80+ each but I got a pair of new 
ones for $20 from a forum member.

Carl
KM1H