Re: tesla coil model

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> 

Tesla list wrote:
 >
 > Original poster: Redmo-at-aol-dot-com
 >
 > Thanks Antonio, for checking my simulation results. I added calculations to
 > integrate the losses in the primary and secondary resistors from time of
 > spark gap firing to first notch and got:
 > energy loss in primary (r1) = .18 joule
 > energy loss in secondary (r2) = .02 joule
 > with so much energy being lossed in the spark gap, I think spark gap
 > resistance reduction could be a major performance improvement area.

Surely.

 > The
 > rotory spark gap may do this somewhat by moving the electrodes closer to
 > each other that the static gap for the same firing voltage.

The spark will occur before perfect alignment, but there is a small
improvement, surely.

 > However as we
 > all know, computer simulations are only as good as the models they are
 > based on. Modeling the spark gap as a simple resistor may not be very good.

Yes, it's just the simplest approximation.

 > I read somewere that the spark gap may have a somewhat constant voltage
 > drop across it when it fires, is this true?

Yes, a spark gap behaves as a gas discharge lamp. In the conduction
region, the incremental resistance is low, and is even negative
for a range of currents. In the region of minimum voltage the voltage
drop is almost constant. The IxV curve is something like this (reflect
both axles for negative voltages and currents):

|I    .
|   .
|  .
|  .
|  .
|   .
|    ..........
|..............       V
+-------------|--------
            Vbreak
But the curve is not static. It moves to lower voltages depending on
the temperature of the gap, not counting other possible effects.
It's not difficult to set up a nonlinear simulation that gives the
observed qualitative behavior, but it's difficult to predict the
correct gap parameters.

Antonio Carlos M. de Queiroz