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Re: DC TC



Gary,

> I found an artical where someone built a large auto transformer that
> produced 42" sparks from a battery power supply.  It's not TC either.

Be interested in seeing more about this.
 
> Many years ago I built a crude Tesla Coil using a DC power supply an 810
> tube and a signal generator to drive the control grid.
> 
> It seem to me if a DC power source could be pulsed at resonate frequency
> it would work fine for a Tesla Coil.
> 
> The next question is what is the best way to pulse a DC power supply
> with out a tube?  How about a DC power supply with an adjustable charge
> rate for the capacitor bank. The discharge rate threw the spark gap
> could be adjusted to find resonate frequency?  The capacitors would have
> to be sized correctly for the proper charge rate.

That implies a real low TC frequency and a real high break rate (CW 
operation). Not a simple proposition. CW operation implies pretty much
continuous secondary loading which means the coil will never attain 
the high voltages you can get in a more slowly pulsed coil. A coil 
operated with, say, one cap discharge per 10 secondary oscillations 
imposes some pretty daunting requirements on both the charging circuit
and gap system. I tried exactly this using a precision (uS type 
precision) pulse generator triggering a MOSFET "gap" on a low powered 
coil during some expts last year. Far from easy even with that gear
and it was stunningly sensitive to objects in the vicinity. I got the
break rate up to that of the coil but the capacitor voltage was 
sagging badly as a result, even with a small boost choke. In fact,
the power supply almost needs to be resonant at Fs as well to do it 
properly. Technically this is approaching Class-C operation.

 > With a Tesla Coils operating on a DC power supply it seem like the
> toroid or sphere on top of the secondary would charge up in one polarity
> like a Van De Graff generator.

It is a power oscillator. It cannot be pumped up DC-wise because the
secondary is a piece of wire connecting the toroid to ground. It has,
as you say, a resonant frequency. You could elevate the entire coil 
DC-wise by inserting a DC supply between ground and the bottom of the 
secondary (a la Greg).

Malcolm