Re: Secondary size - the Why

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Original poster: G <bog-at-cinci.rr-dot-com> 

Hi All,

I'm sure I missed something important, but is the secondary self-C minimum 
at 2.5:1, 3.6:1, or between 4:1 and 5:1?

cya,
Gregory

>Something more realistic would be to ask:
>"For a given inductance to be realized, what is the aspect ratio that
>results in the minimum self-capacitance?"
>This problem can be solved too, using Wheeler's formula for the
>inductance in the form:
>L=u0*Pi*N^2*r/((h/r)+0.9) H
>and considering that the number or turns, N=h/d, where d is the wire
>diameter (or winding pitch).
> From these relations, r can be obtained as a function of (h/r) and
>several constants, and substituted in the formula for the self-
>capacitance:
>C=r*(11.26*(h/r)+16+76.4*sqrt(r/h)) pF
>Finding the minimum (easier graphically in this case), I obtain:
>
>h/(2*r)=2.5781
>
>This minimum does not depend on the wire used, the winding pitch,
>or on the inductance (as long as we assume that the formulas are valid).
>It is a broad minimum, with little degeneration for larger ratios.
>
>For something more realistic, the effect of the top load would have to
>be taken into account, as it reduces the charge density at the top of
>the coil, reducing its effective self-capacitance.
>
>Antonio Carlos M. de Queiroz


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