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Donner und Blitzen


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From:  Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent:  Monday, February 23, 1998 1:02 PM
To:  Tesla List
Subject:  Re: Donner und Blitzen

L.Robertson wrote:


> Why not put a jolly big pulse discharge capacitor
> between the bottom of the secondary and ground.
> Charge it up to many tens of kV, then crank up the
> coil as usual. Any ionization path to ground ought
> to benefit from the energy stored in the big cap.

Indeed, it does!  I tried a similiar experiment 
with a 14uF cap bank at 110kV, as part of a 
schnapps-inspired quickie experiment after an 
SRL show a few years back.  The resulting arc
spanned about 23 feet and appeared to the eye
to be about 6 inches in dia, though I am sure 
that this was just optical bleed on the retina.
The peak current in the arc was about 1600A, and
the arc channel produced a rather satisfying bass note.

> I rationalized that if the big cap had a frequency
> response faster than the coil frequency, capacitve
> division should protect it from voltage breakthrough.

Yes, those big energy storage caps are quite 
oblivious to secondary currents; however, one
has to make sure that the secondary winding can
withstand the rather sharp Lorentz forces that will 
try to expand and 'accordion' the secondary.  This is
why my present coil's sec is wound with heavy 8 ga wire.

> Initial low power testing with six inches of spark,
> but no charge on the big cap revealed an interesting
> phenomenon. If the toroid was shorted to ground, nothing
> happened. When no spark was present, again nada.
> When spark was present though, a slow but steady charge
> built up on the Aerovox. 20 seconds of spark would
> produce about 5000 volts of DC on the capacitor.

There may be some rectification going on in the 
arc; but the exponentially damped output waveform 
of a TC naturally has a non-trivial DC component,
owing to the fact that the 1st, 3rd,..etc haversines
are larger than the 2nd, 4th,...etc haversines.
The bigger the arc, the sharper the damping 
(and therefore the greater the asymmetry).


-GL