Re: Formula for true self capacity of a coil.

["Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Ed,

> Original Poster: "Ed Phillips" <evp-at-pacbell-dot-net> 
> 
> Guys:
> 
> 	I can't understand the interest in great accuracy in  calculating TC
> inductance and capacitance when some of the factors  are not readily
> quantifiable.  For example, the reactive component of streamer loading
> is a non-linear function of time and power being dissipated in the
> streamers.

I am most interested in claims pertain to the resonant mode of the 
secondary when coupled to the primary, issues such as gap 
dwell/quench capability, operating with widely differing pri sec freqs 
as Ken Corum once told me could be (and implied was being) done 
and a host of other issues, all of which must be tested with no 
breakout and hence streamer loading. It is all very well to claim dwell 
times in the order of a few uS for well built rotaries etc. but quite 
another to prove that they can perform some kind of magic if energy 
remains bottled up in the system. Letting secondary sparks out is 
cheating IMHO. Besides, if the streamers drain energy from a 
system, measuring any kind of magical voltage rise following quench 
just isn't going to happen (is it?).

  Most of the simple formulae are quite adequate "for
> government work".  As for "Wheeler's formula", he had more than one,
> their use depending on the L/D of the coil.  Furthermore, in many cases
> a correction for "current-sheet inductance" is needed.  Stuff is all
> available in almost any edition of The Radiotron Designer's Handbook,
> for instance.
> 
> 	For those who might be interested I have written some DOS programs 
> (have Mac versions too) which calculate inducatance to an accuracy
> determined strictly by the accuracy with which the coil dimensions are
> known. Also have same for calculating mutual inductance and coupling
> factor for coaxial round coils such as TC's.  If anyone is interested
> I'll be glad to email them.

Yes - I tried your program with the corrective factors and it worked 
very well. I'd forgotten about that sorry. I remember having to use it 
with highly spaced coils in some tests last year. 

Regards,
Malcolm