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Re: Ganging Caps



---------- Forwarded message ----------
Date: Mon, 29 Sep 1997 20:37:33 +0300 (EET DST)
From: Harri Suomalainen <haba-at-cc.hut.fi>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Ganging Caps

On Sun, 28 Sep 1997, Tesla List wrote:
> points I hadn't thought about. Yes I was calculating equal voltage distribution

In high-voltage systems E-field is the most important thing to think
about. Else dielectrics will break.

> your suggestions and make some actual measurements. I'll post my findings,

Great, I'm interested in this subject further.

> Regarding the electrical field distribution: You talked of encasing each roll
> it's own conductive housing and connecting one side of the cap to this casing
> to limit E-field. Possibly there's an easy way to do this? maybe simply
> wrapping each roll in aluminum foil and connecting one leg to the foil will
> acheive this E-field limiting. Of course I know roll to roll breakdown must not
> occur. What do you think? What does anyone think?

Something like that should do. Perhaps something else like just having
conductive disks every few rolls or something. There are lots of ways
of doing that. Just remember to cover enough way from the edges (so rolls
will not be connected capasitively to air through the end not covered) or
have the ends covered too.

Do try to avoid sharp edges or you'l run into corona problems as well as
more problems with roll-to-roll breakdown preventations.

> I do have specs on these caps from CSI and the inductance is in a range from
> 100 to 200 nH. I'll have to measure this as well with dummy terminals since the
> inductance will be influenced largely by the terminals. Also, William Noble

Also say 5 paralleled rolls making a 200nH will make 5*200nH = 1 uH for
one cap.

Geometry of rolls will effect the total inductance as well. With longer
distances to cover you will easily make inductance of your cap-to-cap
router fairly high. However, in loosely coupled systems like tesla
coils some series inductance is certainly allowable, fortunately.