From: "Terrell W. Fritz"
Date: Sat, 15 Jun 2002 19:35:55 -0600
Subject: Re: [TSSP] Re: Top V Probe Design
Hi Paul,
>
>Terry wrote:
>
>> http://hot-streamer.com/temp/HVProbe-2.gif
>
>For R2 = 0.5" = 0.0127m;
> R1 = 3.0" = 0.0762m;
>and setting E = 6000kV/m at Rx = R1, we have a max
>working voltage of
>
> V = 0.0127 * 6000 * ln(0.0762/0.0127)
> = 136 kV
>
>based on breakdown of the inner capacitance.
>
>For the outer outer shield to the secondary coil, we have
>
> R2 = 3.0" = 0.0762m;
> R1 = 5.5" = 0.1397m;
>
> V = 0.0762 * 6000 * ln(0.1397/0.0762)
> = 277 kV.
>
>So the system is likely to be limited to quite small
>toploads due to breakdown of the inner capacitance.
>
>A larger inner electrode would improve things a little, eg
>
> R2 = 1.5" = 0.0381m;
> R1 = 3.0" = 0.0762m;
>
> V = 0.0381 * 6000 * ln(0.0762/0.0381)
> = 158 kV
>
>but then the total capacitance goes up quite a bit unless
>the inner electrode is made a lot shorter.
>
>I have a modification to suggest, which I'll sketch out
>and post later today. Unfortunately it's quite a large
>modification...
>--
>Paul Nicholson,
>--
Of course, you make a good point about the coaxial cylinders. My original
calculation assumed in infinite area outside the radius of the electrode which
is very wrong in this case.
I am looking very forward to you idea. Quite large modifications are not a
problem since I have quite large "tools" :o))
Interestingly, there are ways of making the thing fault tolerant where an
internal arc will not hurt anything (BIG C2 that absorbs a direct hit).
However, I can also fiber optic isolate it too. That may be worth while since
it allows us to get away with low safety factors. It also isolates "ground"
which is pretty unstable in these things.
It is interesting that no commercial device does things like this. Maybe we'll
invent something new :-)
Let me know what your modification is and we'll se if I can work it in.
Cheers,
Terry
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.