Re: GM HEI (further measurements)

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

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



Tesla list wrote:
> 
> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> 
> At 11:19 AM 1/19/2002 -0200, you wrote:
>   The top load or terminal attached to the high-voltage button affects
> >> the resonant frequency a lot too even though the HV-winding does seem to
> >> have a large natural capacitance associated with it.
> >
> >Would this be really true? Remember that a in a Tesla coil secondary,
> >the self-capacitance of the coil is a function practically only of the
> >dimensions of the coil (one half of the body capacitance of a metal
> >cylinder with the shape of the coil). In an induction coil there are
> >the core and a metal case, that contribute with some extra capacitance
> >to the windings, but these are not so big. An inductance of 10 H
> >resonating at 10 kHz is seing only 25 pF of capacitance. It would be
> >interesting to see measurements of these capacitances, with and
> >without the core and the case.
> >
> >Antonio Carlos M. de Queiroz
> >
> >
> 
> I think the turn to turn capacitance is far higher in these coils.
> 
> http://hot-streamer-dot-com/TeslaCoils/Misc/GMHEI/GMHEI.jpg
> 
> Not a Medhurst distributed capacitance, but lots of wires wrapped together
> in a small place.
> 
> Cheers,
> 
>         Terry

Hi Terry,

While your statement sounds plausible, I'm not shure if it proves true:
for my big induction coil i have to enter ~40pF in the simulation of the
secondary: 

http://home.datacomm.ch/k.schraner/induc_simu.htm


This same value of 40pF gives best representation of the experimental
results, as well, with the (slightly corrected) induction coil theory
from A.Bouwers's book on "Elektrische Hoechstspannungen".
The primary - secondary interwinding capacitance shows ~80pF when
measured with my LCR meter at 1kHz. But this was not included in the
simulations. I can make some measurements, with or without the removable
ironcore of the coil, if that would help further investigations.

Cheers,
          Kurt