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RE: Terry's DRSSTC - Controller Experiment
Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
At 07:30 AM 4/20/2005, you wrote:
>A system operting in this way can always
>be redesigned to produce the same output voltage, and energy,
>faster and with less input current, with notches in the primary
>current and voltage.
Yes, but I don't think this makes it any more efficient at spark production.
The reason being that streamer loading throws all the theory out the window.
Streamer loading is really not super heavy compared to the coil's own
impedance. Losses will cause variation from Antonio's models some, but I
think those models will still be fairly good. I think given a choice, it
is best to try and make a magnifier that follows Antonio's models for best
transfer. I certainly don't see how it could hurt. Antonio's models are
just about all we have to go off of anyway ;-)
Antonio's theory assumes that breakout doesn't happen until the very end of
the burst. But with the current trend for big sparks out of small coils,
breakout happens early. Hence the total energy delivered to the streamers
can be maybe 6 times more than what the topload can hold when charged to its
breakout voltage. This is a radical departure from traditional TC theory and
you need to think about it for a while. But I believe it is true for DRSSTCs
and probably for high powered spark gap coils too.
The coil is only really lossless for maybe 80% voltage on the very first
bang. After that, the streamers will reduce the arc out voltage
drastically. The DRSSTC can certainly drive power for as long as it want
to during a bang since it is fed from an infinite source or until the IGBTs
blow up. It might be a "next step" to try and "modulate" a DRSSTC to give
a constant voltage output for say milliseconds. If you stay within the
IGBTs "normal" load range, the voltage could be maintained
indefinitely. Maybe like a single bang that lasts two days ;-))
BTW - Thanks Steve Ward for making the definitions! I hope I am learning
to use them right. I think we need to add "Repetitions" for the number of
bangs in a burst...
If I understand right, a coil designed to Antonio's theory can never produce
a bang energy bigger than the charge the topload can hold, so it would look
pretty wimpy in comparison to the tabletop coils Steve made that spark 3
times their own height :-o That is why we tend to stay with self-resonant
operation at the poles.
Antoinio's stuff never considered a none energy limited power source (who
would have ever thought...). However, that should not be too hard to
reconsider now that the DRSSTC is here.
Anyway, once the secondary is loaded by streamers the whole behaviour
changes. With a heavy enough load the two resonant peaks get damped out and
the whole Antonio vs. Ward thing becomes a non-issue- to keep the sparks
growing you just need to drive a frequency somewhere within the "bandpass"
of the "filter".
So, you could have a "hybrid" mode that uses Antonio mode to ignite the
initial breakout and then continues driving to make up any desired bang
energy. The resulting waveform would have a single notch followed by a flat
But the control circuitry to do this reliably with feedback is difficult
(you may need to change the feedback phase mid-burst) I have done it on the
bench without feedback but the tuning was incredibly sensitive and it only
took the slightest change to make the notch disappear. So I guessed it would
be too sensitive to streamer loading and went back to the plain
This is what my DRSSTC does all the time:
In the top waveform the current normally switches every 5uS. But in the
middle there is a 7uS pause. In the lower waveform I have a ~15uS
pause!! Goodness knows what the phase and frequency/time shifting looks
like. But I use pure current to control the timing so it is not a problem
in my case.
My DRSSTC will be lighting up soon- hopefully from its top and not from the
Cool!!! I am wondering if I need to reprogram to get to like 10000
BPS.... Not sure the present microcontroller can do that... Also have to
dig up the old Magnifier parts ;-))