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Re: Tesla Coil toroid Size

Hi all,
        Some thoughts FWIW:
        

> Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>=20
> 
> 
>   Reinhard -
> 
>   The spark characteristics such as brilliant white core are dependent on
> the current but only the voltage determines the path of the spark length.

In the case of repetitive sparks I'd have to disagree. However.....

> Of course, the properties of the air or gas will also affect the spark
> length and appearence.
> 
>   I believe what Brent Turner was referring to was the fact that the
> calculated capacitance of the toroid or sphere is not the capacitance tha=
> t
> the toroid or sphere has when placed on the Tesla coil. The presence of t=
> he
> coil and other objects lowers the capacitance about 15% to 30%. This is o=
> ne
> of the reasons why the TC has to be tweaked after it is properly designed
> and built.
> 
>   There is no way to determine the effective toroid capacity on the TC at
> the design stage. However, in the information with my books I show a meth=
> od
> of finding the exact effective capacitance of the toroid or sphere on the
> TC after it is built and tested and using the JHCTES computer program.=20
> 
>   John Couture

There might not be a way yet but that is simply because no-one has 
yet produced a formula that takes the size of the seocndary coil into 
account (you obviously cannot use figures for an isolated 
sphere/toroid yet that is what all formulae I've seen have done to 
date ;)

     Here are some figures for some different coils I have measured. 
These figures are not the last word because isolation was not as 
great as I would have liked for definitive measurements, but here 
goes:

Terminal 1  (fairly large, toroidal profile, no centre hole)
Terminal 2  (smaller, same shape)
Terminal 3  (much smaller, same shape)

Dsec    Hsec     Csec     Cterm1    Cterm2     Cterm3

3.5"    14"     6.4pF     39.4pF    29.3pF     18.5pF
4.4"    17.2"   7.9pF     36.2pF    26.6pF     16.2pF
4.8"    21.8"   9.4pF     31.6pF    22.7pF     13.4pF
6"      22.7"   10.7pF    33.3pF    23.8pF     13.8pF
6.7"    12.1"   8.4pF     40.2pF    29.7pF     18.4pF 
6.7"    19.8"   10.3pF    38.4pF    27.9pF     16.9pF 
6.7"    32.3"   13.5pF    34.1pF    24.2pF     13.8pF
9"      16.1"   11.2pF    31.7pF    22.8pF     13.6pF
16.7"   39"     22.9pF    30.1pF    21pF       11.9pF

     Note the variability. I gathered these figures solely for 
designing primaries for these coils (knowing Fr). The capacitances 
were calculated as a matter of interest. They may not even be true 
capacitance figures as shorted turn coupling into the shorter 
resonators might be a factor. Draw your own conclusions.

Malcolm
<snip>