Re: Formula for calculating self resonant frequency of secondary coil or helical coil?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
 >
 > Original poster: "Ed Phillips by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

 >  > Hello everyone, I was just curious, I know there are programs out there
 >  > that calculate the self resonant frequency of a secondary coil, like
 >  > wintesla etc. But does anyone know the actual equation the programs 
use? I
 >  > would like to know so I would be able to find the frequencies without
 >  > having to use a computer and the like
 >
 >         Sure.  Most just use one of Wheeler's approximations for 
inductance and
 > some form of Medhurst's approximation for self capacitance; simple pen
 > and pencil or calculator job.  If you or any other interested person can
 > read BASIC code I can sent you the text source file for a BASIC program
 > that does exactly that.  Equations are obvious from the listing.

To see how accurate the popular Wheeler formulas are, you can use my
program Inca (http://www.coe.ufrj.br/~acmq/programs).
I have implemented a very precise (low frequency) inductance
calculation method there, along with several other accurate formulas.
The program list the Wheeler approximations too. They work very well
for solenoids with tightly spaced turns (current sheet model), and
quite acceptably for flat spirals. Even the approximation for conical
coils is not so bad.

Antonio Carlos M. de Queiroz