----- Original Message -----
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
To: <amps@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
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