Re: Lightning Arrestors (was Geek Pig)

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Luc,

It appears to be a single sintered cylinder about 3" in diameter and 9"
long. 

-- Bert --

Tesla list wrote:
> 
> 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!
> > >
> > > _________________________________________________________________
> > > Get your FREE download of MSN Explorer at http://explorer.msn-dot-com

-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com