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Re: OL-DRSSTC - 13

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:
Original poster: Steve Ward <steve.ward@xxxxxxxxx>

As expected, the burst shortens up so most of the real power is in
the first 400uS. This is an interesting tuning spot since you can
see the modes switching between poles as the streamer forms.
I think the beating is just because you are exciting both frequencies simultaneously, but usually one or the other is more dominant, so you dont get full cancellation when the 2 frequencies cancel. Just do an FFT on your primary current and you should see the two peaks, one of them being smaller (usually the upper pole is smaller). So i dont think its "switching" between poles, but rather, exciting them both at the same time. 

These beats are caused by the transient involving the excitation
frequency (almost constant) and the two natural oscillations of the
system. Even if the excitation is at exactly one of the resonances,
there are beats with the other.

I notice for small DRSSTC's that tuning the primary extra low, so as to just about eliminate the upper pole allows for more energy to be *quickly* delivered to the spark. You no longer get a beating waveform (indicating energy transfer back and forth), but rather the primary current builds linearly over many cycles until finally, the secondary can zap it all out (at which point you do get a steep dip in primary current). Im not sure if the OL-DRSSTC can take benefit of this tuning. In my smaller DRSSTCs im limited to maybe a 24" spark with tunings that cause the beating effect, but when i detune it to get only one "beat" i can do 37". This whole scheme doesnt seem to matter for big coils, since it seems you can deliver enough energy in a few cycles anyway, so one normal "beat" is usually enough. 

This "one beat" in the primary current until breakout corresponds
to excitation exactly between the two resonances, that is where
a system with primary current feedback tends to lock too (if the
system is designed for this).
Theoretically, this is really the tuning that produces faster energy
transfer and maximum efficiency, assuming that the driver is not
kept in operation for much time after breakout. Anyway, if it is kept
operating, the input current rises again from zero, and the driver
can operate for more time before the current grows excessively.
See http://www.coe.ufrj.br/~acmq/tesla/drsstc.html

Antonio Carlos M. de Queiroz