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> Subscriber: gweaver-at-earthlink-dot-net Sat Feb 15 15:43:29 1997
> Date: Fri, 14 Feb 1997 20:43:14 -0800
> From: Gary Weaver <gweaver-at-earthlink-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: DC TC
>
> It seems 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.
>
You can use a DC supply to power a Tesla coil, but you
have to be very careful and make sure you use a diode or diode array that
is capable of handling the full, worst-case reverse voltage. And
believe me, it is higher than most people think! A 12KV transformer
will charge the capacitor to about 16.8KV Peak. When the AC reverses
polarity the voltage across the diode goes to 33.6KV. Stress factors
like this represent the *minimum* that you should expect. These peak
values will occur up to once each cycle of the main AC frequency (60Hz).
Always multiply such values by at least 1.5 (and preferably by 2) to
arrive at a decent safety margin. I would use a 50KV diode as a minimum
rating for use with a 12KV transformer. In my saner moments I would
want a rating of at least 66KV for the diode.
The current rating should be at least 1 amp if you are using a constant
current neon transformer rated from 30 to 120 ma. Again the motto is
"better Too Big than Too Bad!"
You should use Chokes to protect the diode/transformer.
The "adjustable charge rate" is not necessary. The Spark gap takes care of
delivering the current at the proper moment, which is whenever the actual
voltage reaches the Spark gap breakdown voltage.
The frequency of oscillation is determined by LC, not by any other
factor.
Unless you use a full-wave bridge diode arrangement, you really
don't gain much operationally. With a full-wave bridge you at
least get to have 120 Peaks per second instead of just the usual 60.
What we really need here is to hear from those who have actually built such
beasts.
OK, guys, you who have actually *done* all this DC stuff, is it
worth it at all? Or is it a big bust???
> 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. Would the Tesla Coil produce longer and
> more powerful output sparks at resonate frequency from DC?
>
No, The Tesla coil will oscillate due to the tank circuit. It will be AC
out, *not* DC.
> Gary Weaver
Fr. Tom McGahee