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Re: [TCML] Bipolar tesla coil



On 12/23/12 11:53 PM, Kurt Schraner wrote:
-----Ursprüngliche Nachricht----- From: Jim Lux
Sent: Sunday, December 23, 2012 11:50 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Bipolar tesla coil

On 12/23/12 10:48 AM, Kurt Schraner wrote:
A fairly complete report about my version of a bipolar tabletop coil can
be downloaded here:

http://twfpowerelectronics.com/~kurt/EBM-Museums-TC-2.pdf

A very pretty coil.

about 1000 turns on the 2 1/2" x18" secondary, 5 turn primary tapped
down to 4 turns. 18nF primary C.

I like the three pipe gently blown gap (because I use one identical to
it!).. for low power coils, I've had good luck.. it's more easily
adjustable than a two pipe gap, it's only two gaps, so gap losses are low..

That's a fairly high current low voltage NST compared to typical
practice here in the US (it's like a 12kV 60 mA in terms of power..) so
you might want to change the primary L and C a bit to match your
transformer, while keeping the resonant frequency in the same
ballpark... (bigger L, smaller C)
_______________________________________________

Thanks Jim, for the friendly comment. Concur about the 3-pipe gap. But
to match the cap to the NST, in direction resonant or LTR, i would need
to make it bigger, not smaller. The cap is STR, and the NST would be
able to charge a much bigger cap. But there i had to make a compromise,
in order not to obtain a smaller than 1 turn primary. Or did I
misunderstand you, and you had something different in mind, as a
matching goal?
\

I was thinking that if you were building this coil in the US with a 15kV, 60mA transformer, you would go with a smaller higher voltage capacitor (so that it charges in the same amount of time), and the primary L would need to be bigger, to keep the resonance about the same.

I didn't catch that the cap is much smaller than resonant, so you could leave it the same with a higher voltage/smaller current transformer.


Yes, I can see the need for compromise.. a high current transformer pushes you to a big capacitor and a small inductor, and I'd hate to have to try and tune a 1 turn inductor. It's one thing to move 1/8 turn on a 5 or 10 turn inductor.. it's a small percentage change in L. But even a small change in the relative lead wire position would change the inductance of a 1 turn.

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