From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Wednesday, February 23, 2000 6:59 AM
>Original Poster: "Christopher Boden" <chrisboden-at-hotmail-dot-com>
>As I understand it a MOV (Metal Oxide Varistor) is basically a whomping
>Zeneer Diode in essance. It does nothing untill you reach a prescribed
>voltage, then acts as a short circuit. A hogh voltage gate essentially. Am
Yes, basically, although MOV's have a distinct life characteristic (every
hit reduces the remaining capacity,until they fail)... Don't forget that
while they conduct, they dissipate a fair amount of power (That is, say
you've got a 440 V MOV and your spike is 1 amp... that's 440W it's
dissipating..) It used to be Harris that was a big mfr of these and their
web site had a lot of info, but they've changed names, and I don't recall
who does the MOV's now.
>Assumeing I am right (hey, this is my dream remember?) then how is this
>different than a spark gap?
The spark gap, once it starts conducting, has a very low on resistance and
on voltage... The MOV still has a high voltage across it...
>Do they reset after use? or simply short out and need to be replaced.
yes they reset...
>If these behaive like a gap, then why use them in place of a gap in an NST
>protection circuit? pros/cons?
Slow, lots of power dissipation when they are conducting.
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