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Re: Tesla Coil toroid Size
Hello John,
> Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>
>
> Malcolm -
>
> Thank you for the toroid capacitance data from your measurements. I
> thought you would be interested in what I caculated. The following
> information is based on methods that have not been completely verified.
>
> The "In space" capacitances are from theoretical equations. I show a
> graph in one of my books based on these equations. The "On TC" capacitances
> are estimated for your toroid but based on what I have found from other
> coilers tests. Note that the toroid capacitance is reduced by the presence
> of the coil.
>
> In space On TC
>
> Toroid #1 - 11 x 30 33 pf 26 pf
>
> Toroid #2 - 10 x 23 28 pf 22 pf
>
> Toroid #3 - 6 x 19 22 pf 17 pf
There is some clear difference between your theory and practice here
because the isolated values you calculate for T#1 are less than what
it actually adds to a number of coils.
> I would expect differences from your values because the tests differed.
> The above results (On TC) would be obtained by finding the actual operating
> frequency of the TC and using this info to find the effective capacitance
> of the toroid.
Exactly what I did. If tests don't agree then something is wrong with
either one or both tests. There is a high degree of consistency in
what I measured if you check for incremental differences between the
capacitances as measured.
> Cs = 1/(39.5 Ls F^2) and Ctor = Cs - Ccoil
Which is not a great deal of use for predicting prior to the fact as
you said. For some time now I have viewed the situation as being the
capacitance of the total structure. As you say, the presence of the
coil reduces Ctop by some amount and I suspect that amount is a
function of the effective area (sides and bottom) of Ctop as a
proportion of total structure area. That includes shading by the coil
of the bottom of Ctop. Interesting to note that a 6"x2" top place on
the 16.7" dia coil doesn't add a jot of capacitance to the coil.
Csec is easily and accurately calculated using Medhurst's formula.
Malcolm
<snip>