Spark Gaps

From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
Sent:  Friday, April 10, 1998 10:26 AM
To:  Tesla List
Subject:  Re: Spark Gaps

> ----------
> From:  Antonio C. M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
> Sent:  Thursday, April 09, 1998 1:11 PM
> To:  Tesla List
> Subject:  Re: Spark Gaps
> Jim Lux wrote:
> > 3) Faster interruption of the spark. As opposed to just waiting for the
> > current to go through a zero, the gap is physically separated. The
> > circuit opening causes the voltage across the primary inductor to rise,
> > inducing a similar rise in the secondary. The faster the interruption
> > (di/dt) the more the rise.
> Do this really work? This would be like operating a Tesla coil as an
> induction coil. The theory saying that there is a great increase in the
> secondary voltage or a two-coil system after the opening of the spark
> gap (Corums) may be due to this effect (otherwise I don't see how).

I have no theoretical basis for my statement, above. It was proposed as a
possible reason why one might want a rotary gap. The other, related, theory
I have come across has to do with the energy transfer back and forth
between the primary and secondary. The idea being that if one removes the
resonant primary at a time when the energy is mostly in the secondary, then
that optimizes the performance: as opposed to letting it dissipate as heat
in the primary.

Interestingly, with a static gap, I wouldn't expect the gap to "open" at a
current maximum, the contrary, in fact, resulting in essentially ZERO
di/dt. With a rotary gap, one could conceivably interrupt the arc (by
stretching it long enough) while significant current is still flowing
through the arc. Now, the di/dt is pretty significant. 

I'm too lazy to go back through everyone's posts on modelling the coil, so
I'll ask a redundant question: Have you looked at this aspect of the
gap/primary circuit? Say you modeled the gap as a perfect switch that opens
and closes in some sort of synchronism with the primary waveform, what sort
of waveforms are created? in a theoretical sense, at least.