Re: toroid dimensions

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Esondrmn-at-aol-dot-com>

In a message dated 9/25/01 12:52:13 PM Pacific Daylight Time, tesla-at-pupman-dot-com
writes: 


>
> Hi all, 
> Is there an optimum physical size for the topload terminal?  I bought some 
> 4" dryer duct planning on making a 22" total outer diameter toroid for my 6" 
> x 24" secondary (27.5mH).  Using a 15/60 NST, a 10.5 turn .4" spaced 3/8" 
> copper tubing primary (56.9uH).  The topload capacity should be 23pF 
> (WinTesla) giving me 164.6 kHz res freq.  I've read descriptions of other 
> coils similar to mine with and I'm concerned my toroid may be too small.  Is 
> there a way to measure its capacitance?  I have a signal generator and scope 
> at home.  I've read about using a "grid dipping" method to measure primary 
> and secondary resonant frequencies for tuning.  Maybe you could measure the 
> secondary without toroid and then with to deduce topload cap.  Anyone tried 
> this? 
>
> Jeff Johnson 
>
>
> Jeff


, 


Your coil is similar in size to mine.  I use two toroids, one 6" x 33" and one
6" x 40".  You want the largest toroid that the system will breakout.  I used
smaller toroids when the coil was first built and then went to increasingly
larger sizes as I scaled up the input power - now running at 7kva.  I know of
no method of measuring the toroid capacitance directly.  I have only used
calculations.  Your plan of measuring resonant frequency with and without the
toroid, then calculating the toroid capacitance sounds like a good plan.  You
can see my set up at: 
http://members.aol-dot-com/esondrmn/index.html 

Ed Sonderman