RE: Secondary Topload ( was New formula for secondaryresonant frequency)

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

Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net>


Kurt -

What I was trying to point out was that your measured 69 Khz was very close
to the JHCTES output of 69.59 Khz. In the past some coilers said that their
measured frequency was much different than the JHCTES and, therefore, the
program was incorrect. It now appears that the coilers inputs or
measurements where incorrect.

The JHCTES program does not use Bert Pool's equation. I found this equation
did not give accurate enough toroid capacitances compared to measures
results. The JHCTES program uses instead the two equations by F. Lowenstein
shown in the TCBA Newsletter for April, 1987. In one of my books I show a
capacitance graph based on these equations for different size toroids. These
graph capacitances can be used in the JHCTES program. The graph has the
advantage that you do not need to do any calculations to find the toroid
sizes when you know the capcitance values.

It should be noted that any computer TC program will only be approximate
because the outputs are dependent on the accuracy of the inputs. At present
it appears that the ion cloud and other effects would not change the outputs
by more than +/- 5 percent.

John Couture

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-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, February 08, 2001 6:54 AM
To: tesla-at-pupman-dot-com
Subject: Re: Secondary Topload ( was New formula for secondaryresonant
frequency)


Original poster: "Kurt Schraner by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<k.schraner-at-datacomm.ch>

Hi John,

I'm not shure, if I get you right: isn't it widespread design
practice, to calculate the loaded secondary Fres by just adding
the Medhurst coil-capacity to the independently estimated toroid
capacity (by Bert Pool's equation), then estimating the
inductance by wheeler's formula, and then calculating the
resonant frequency by the Thomson formula ? In symbols:

Cmed = (H/D)*K  (with K from the Medhurst table or a fit eqn.)
Ctop = (1+(.2781-d2/d1))*2.8*sqrt(pi((d1-d2)*(d2/2))/2)  Bert
Pool's

Csec = Cmed + Ctop  <--- point of concern ??

Lsec = (R^2 x N^2) / (9R + 10B)    Wheeler
Fres = 1/ (2pi*(sqrt(Lsec * Csec)) Thomson

...at least it's the way I'm doing it. I'm aware, that the
addition of the C's is not ultimately correct (as Paul
Nicholson's detailed analysis shows). And when the coil comes to
breakout, the topload is in fact expanded by the sparks and ion
clouds...

Soo..., are you meaning, you are using an empirical rule, to
combine the two capacitances in a more suitable way? I would be
most interested in it. My calculation, presented in the same way
as yours from JHTES 3.2, are:

 For the Primary I entered
  Cap = 0.1094 uf,  Avg Rad = 13.335, and  Width = 6.984
 For the Secondary I entered  Rad = 7.9,  Turns = 821,
   TPI = 11.80,  and  Sec Term = 69.59 pf
 The operating frequency was 67.93 Khz,  Pri Ind = 50,16 uh,
   Pri turns = 7.12, etc.

The difference is not very big, but you are closer to the
measured loaded Fres of 69kHz. But what is fairly strange: your
predicted Fres is HIGHER than mine - not LOWER, what I would
expect from ion clouds etc.-. So, your capacitance combination
rule would need a subtractive part?

Greets
Kurt Schraner

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