Re: Get it over with

To: tesla-at-pupman-dot-com
Subject: Re: Get it over with
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
Date: Mon, 3 Feb 1997 16:35:19 -0500
Subscriber: tom_mcgahee-at-sigmais-dot-com Mon Feb 3 21:39:48 1997
    [The following text is in the "ISO-8859-1" character set]
    [Your display is set for the "US-ASCII" character set]
    [Some characters may be displayed incorrectly]



----------
> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: Re: Get it over with
> Date: Sunday, February 02, 1997 8:25 PM
> 
> Subscriber: ax-at-href-dot-com Sun Feb  2 17:27:39 1997
> Date: Sat, 01 Feb 1997 22:58:44 -0800
> From: Michael Ax <ax-at-href-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Get it over with
> 
> At 10:10 PM 2/1/97 -0700, you wrote:
> ..
> >Yes. You don't want to waste any of the stored energy, so corona
reduction
> >via a curved electrode is indeed desireable. Without some form of safety
> >gap an expensive capacitor can be ruined in a fraction of a second. Even
if
> ..
> >
> 
> Tom --- 
> 	how does one calculate the width of such a 'protection' gap? 
> 
> Michael

Michael,
I have always used an experimental approach to such things. I build a gap
using 3/4" or 1" diameter brass balls. I got mine from a scientific supply
place... something like Fisher or Cenco. The ones I got were threaded and
so easy to attach to a machine screw of same size and pitch. I usually have
one fixed and the other variable. They go right across the cap leads. I
start off with the gaps set in too close. That makes them arc on purpose.
Then in a working machine I mount the cap and make the gap wider and test
and wider and test until it is running the machine correctly and not
arcing. Now if you pull back the Tesla spark gap, the local cap Gap will
fire to protect the cap. Similar caps can be gapped the same. Once I have a
gap properly set I normally fix it in place permanently. The gaps hardly
ever fire, so I use a double nut and fingernail polish as an agent to keep
the nuts from accidentally shaking loose.

Remember it is a protection device. There is a fair amount of leeway as to
the proper setting. I tend to be a bit conservative, because I would rather
have an occasional Cap Gap fire than have a Cap go up in flames (so the
speak). 

Some books give ball gap ratings, but that is really for DC, and is off for
RF use.

Fr. Tom McGahee