RE: Parallel resonant DRSSTC Longer

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>

>Same power to the load.  One is fast and high current.  The other is slow
>and 1/2 the current.  Which one will give better sparks?

Well I believe the fast, high current one will but only up to an extent. The
reason being that streamer growth seems to occur on a timescale of about 100
to 200 microseconds. Hence, any pulse longer than about 200uS seems to just
make the streamer thicker and hotter, not longer. And likewise, any pulse
shorter than 100uS is wasteful of peak current (as you need higher current
to get the same bang energy)


>I would guess that disrupting a happy CW or gently rung up coil somehow
>"rips" an arc air into the air.

That doesn't fit my mental model of things. To me, disruption is only
important in that it gives higher peak power for a given average power and
thus longer sparks for a given power input. In my view of things, all that's
needed for long sparks is a high voltage developed on a low-impedance
resonator. The voltage must be high enough for breakout, and the impedance
must be low enough that the load of a big streamer doesn't drag the output
down.

So, if the voltages and currents used in DRSSTCs could be sustained on a CW
basis then I'm sure the arcs would be even longer and more impressive. But
it wouldn't be practical. Steve's big DRSSTC would pull 300kW and catch fire
in about half a second. Oil cooled resonator anyone :-o


>The OLTC helped a lot, but it was just "too different" from the typical
coil.
>Even though we did not learn much from it

I think we learned a lot about the capabilities of IGBTs and how to drive
them. And we found one way not to build a pulsed SSTC :-\


>One can almost sit at a Godlike computer control
>panel and fiddle with parameters at a whim.  Imagine an experiment like
>Paul's big computer studies of coils.

Yup, with adjustments for DC bus voltage, burst length, and rep rate, you
can control almost everything you might want to. A lot of experimenting
around has been done already, and the 100 to 200 microsecond rule of thumb I
quoted is a result of that. Hopefully there will be lots more empirical
findings like this, and one day someone will do a proper test of an
empirical DRSSTC against an optimal one built according to Antonio's
formula.


Steve C.