Re: [TCML] Primary selfC

["Chris Swinson" <list@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Phil,

> > C = 0.2248*k*A*(N-1)/(d*x)  (in pF)
> where
> k = Dielectric constant (1.0006 for  air)
> A = Effective plate area in square inches (length  x width)
> N = Number of conductive plates (3 for a  rolled cap)
> d = individual dielectric film thickness  (.03937" in this case)
> x = number of stacked sheets of  dielectric between plates (1 in
> > this case)
>
>
> So if the effective capacitance is as 1/4 of that  of a single
> turn-to-single-turn coil, using the above I calculate around  200pF. Still 
> I bet in real
> life it's much less than that!
>
> > I think Chris is looking at about 6.4nF for the ribbon primary.
>
>
>
> If we could get that much capacitance out of  reasonable ribbon primaries, 
> we
> wouldn't bother with primary tank caps!


I think Bart had a typo in the last line, it should be 1mm not 1inch for the 
dielectric... if it was 1" apart then it probably would be in the order of 
200pF.... ( I got 268pF ) Though my primary is 1mm spaced (only running low 
voltage as its a solid state design) and there is 25foot of primary length 
2" wide.. equates to 600 square inches in total, but slightly less will be 
needed to obtain 4 turns at about 22" dia.. pretty much I get tot he value 
of 10nF for 4 turns.



Chris




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