Re: Lightning Arrestors (was Geek Pig)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ludev-at-videotron.ca>

Hi Bert

Is the silicon carbide is just pack down or bind in a kind of ceramic?

Luc Benard


Tesla list wrote:

> Original poster: "Bert Hickman by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>
>
> Chris,
>
> I've take a few pictures of the 9 kV Pyrex Arrestor. These include a
> shot of the whole arrestor (about 15" long), a close-up of the chain of
> spark gaps, and a close-up of the silicon carbide MOV. Arrestors made
> from a combination of Silicon Carbide and spark gaps were commonly used
> from between 1930 and 1970. They have more recently been supplanted by
> Zinc Oxide MOV type. The pictures can be seen at:
>
> http://www.aquila-dot-net/bert.hickman/photos/arrestor1.jpg
> http://www.aquila-dot-net/bert.hickman/photos/arrestorgaps.jpg
> http://www.aquila-dot-net/bert.hickman/photos/arrestorMOV.jpg
>
> -- Bert --
> --
> Bert Hickman
> Stoneridge Engineering
> Email:    bert.hickman-at-aquila-dot-net
> Web Site: http://www.teslamania-dot-com
>
> Tesla list wrote:
> >
> > Original poster: "Christopher Boden by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <chrisboden-at-hotmail-dot-com>
> >
> > Interspersed.....
> >
> > >Original poster: "Bert Hickman by way of Terry Fritz
<twftesla-at-uswest-dot-net>"
> > ><bert.hickman-at-aquila-dot-net>
> > >
> > >Chris,
> > >
> > >Turns out they ARE a bit more complicated than that - remember that
> > >arrestors are designed to provide a safe path to ground for HV
> > >transients, but should open back up once the surge has gone. They must
> > >be able to rapidly recover and hold off normal line voltage. Ideally,
> > >they should pull little or no current at normal line voltage.
> >
> > Thus a spark gap would be the perfect, cheap, simple solution. That's
why it
> > made sense.
> >
> > >
> > >To meet these requirements, most arresters are actually a combination of
> > >spark gaps and MOV's, with the MOV element actually made of silicon
> > >carbide. I happen to have a clear glass 9 kV (Pyrex) arrestor that I use
> > >for demos - it has a MOV that's about  9" long by 3" in diameter, in
> > >series with eight spark gaps (each about 1/16"). Will be interesting to
> > >see what you find inside yours... :^)
> > >
> > >-- Bert --
> >
> > It's killing me........I'm half temped to accidently "drop" it to open
it up
> > :) I have a pair of the little ones, so I can open one, but they're REALLY
> > proud of their sealing mechanisms. The big ones have what looks to have
once
> > been a liquid (like tar), and poured in around the base. The insulator
> > actually sets inside a 4" deep aluminum base, and is held in with this
black
> > nastiness. It works like glass, very brittle, powdery when it shatters, has
> > a grainy, flaky property (like creosote, flint, or mica) and smells
terrible
> > when filed. What IS it? and how do I get rid of it? I want to open this
> > without destroying the insulator....and cutting the case does not look like
> > fun as I don't know what's on the other side.
> >
> > I hate a puzzle in progress. :)
> >
> > Thank's for the info, I could use any MOV inside, but it still doesn't make
> > any sense to me why they would go to the trouble (and expense) of building
> > anything more than a simple spark gap in a sealed container (these don't
> > appear to be vented in any way).
> >
> > Can the gaps be used as a static gap? What are they made of?
> >
> > Constantly learning......constantly changing opinion :)
> >
> > Christopher A. Boden Geek#1
> > President / C.E.O. / Alpha Geek
> > The Geek Group
> > www.thegeekgroup-dot-org
> > Because the Geek shall inherit the Earth!
> >
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