Re: [TCML] Tesla's topload

[Steve Ward <steve.ward@xxxxxxxxx>]

My experience with using both solid and ring toroids is that the capacitance
of my ring design was only about 10-15% less than the solid toroid.  This
was for a 42" OD x 10" cord toroid using 7 x 1" rings (so roughly 50% of the
surface area was metal).  Of course using more rings approaches the same
capacitance of the solid surface toroid.

Jay's logic is pretty much in agreement with mine, but i wouldnt have said
this is a "drastic" decrease in capacitance, but rather a "slight" decrease,
and maybe his mental model exaggerates the effects of shielding and surface
geometry.  I of course used FEM to do a study for optimizing my ring toroid
for parameters like total capacitance, breakdown voltage, material cost, and
labor.  FEM removed the need for me to guess at the charge distribution, it
let me see where i was most likely to get breakout.  For my design, 7 rings
worked out to be the best compromise i thought.  Indeed the breakdown
voltage is lower as rouge sparks from the end opposite of my breakout point
are more frequent than when i used my "solid" toroid (corrugated tubing with
foil tape).  The spark performance is still just as good, though.

Once again, you can get free 2d FEM software from:

http://www.femm.info/wiki/HomePage

Tesla coils are solved using an axis-symmetric solver, in case you were
wondering how to handle it in 2D.  Unfortunately, this means you cant handle
something like Tesla's bumped topload, need actual 3D for that.

Steve


> This is all for a mostly solid object though.
> For a ring toroid the effective capacitance decreases, because of the small
> element size the shielding plays a really important role in how the charges
> are distributed.
>
> is the charge going to be directly between two elements, no because that is
> an unstable situation.
> what about on the interior of the element array, not so much because that
> would not jive with Faraday's laws
>
> so you are limited to the charge having a maximum on the outermost
> conductor that will decrease as it approaches the hypothetical surface the
> elements are trying to make.
> this drastically reduces the surface area and thus also drastically reduces
> the capacitance
>
> Thanks,
> John "Jay" Howson IV
>
>
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