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

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

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

Tesla list wrote:
> 
> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net>
> 
> Kurt -
> 
> I visited your web site and entered the numbers from your B&W coil into the
> on line JHCTES Ver 3.2 computer program. It appears that your coil's top
> load capacitance does not change when placed on the secondary. This
> contradicts past belief that the topload changes when on the coil because of
> ion clouds, etc. Maybe it was because in the past the program inputs were
> not accurate enough and the tests were not precise enough. This is something
> that will have to be researched with further tests.
> 
> For the Primary I entered  Cap = 0.1094 uf,  Avg Rad = 13.335, and  Width =
> 7.0
> For the Secondary I entered  Rad = 7.9,  Turns = 821,
>   TPI = 11.79,  and  Sec Term = 69.59 pf
> The operating frequency was 68.72 Khz,  Pri Ind = 49,03 uh,
>   Pri turns = 7.12, etc.
> 
> The Sec Term = 69.59 is the calculated pf for the toroid you used and also
> agrees with the Toroid graph I show in one of my books. No change was made
> in the capacitance for ion cloud or any or condition.
> 
> John Couture
> 
> ------------------------------
> 
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Sunday, February 04, 2001 12:03 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: New formula for secondary resonant frequency
> 
> Original poster: "Kurt Schraner by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <k.schraner-at-datacomm.ch>
> 
> Paul -
> 
> thank you very much for the good news about usefulness of my
> results. I'd like to give you the most complete experimental
> doc's of my coils, ...but, if it comes to precision: it's a
> bottomless pit! ;o). Even geometric data appear doubtful!
> 
> >Paul wrote:
> 
> <snip>
> ...
> > Agreed. In the case of the B&W coil, the lack of a well defined
> > ground surface provides an ambiguous termination of the external
> > E-field, so the coil is outside the domain of the formula.
> 
> In fact, all my measurements suffer from this shortcoming. The
> situation for B&W may be seen at
> 
> http://home.datacomm.ch/k.schraner/bw_sec.htm
> 
> ------------------------------   snip
> 
> Best regards
> Kurt Schraner