RE: SSTC modelling- any math geniuses?

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

Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com> 

 >That is the real problem and gets much worse when the streamers
 >connect with a target.

Ordinary untuned primary SSTCs that I and others have built, seem quite
happy when the arc connects to ground. The current draw decreases, and in
the limit when the toroid is shorted to ground, the current draw from the DC
bus is nearly zero.

OTOH, the new DR and ISSTCs are capable of going "nuclear" when shorted out
by an arc to ground. The low impedance at the resonator top transforms to a
near infinite impedance at the base, and the tuned primary sees no load,
allowing the primary current to ring up without limit.

We get round this one by running them in pulsed mode, ie the inverter
operates for say a 200uS burst every 10ms. Even if the secondary was totally
shorted, 200uS is not enough time for the current to ring up to _really_
scary levels. But it can still cause a higher than normal current, hence not
a good idea to totally short one of these coils out with an arc to a very
close by target. (A long arc to ground has more resistance and can dissipate
power safely.)

The primary current can also increase without limit if breakout does not
happen, but this is less of a problem, it usually just ends in a pri-sec
flashover rather than IGBT-Ma-Geddon. After all, the secondary voltage
increases without limit in this case too :)))

Anyway, somewhere in between these extremes of "totally short" and "totally
open" there is a streamer load impedance that leads to optimum power
transfer. Richie and I are working on a design procedure that will let you
start by specifying what length of streamers you want, then work back to
find the primary L/C/k you need to match your inverter to that particular
streamer load.

It will also tell you the peak primary current, hence what size of IGBTs you
need. And if that turns out bigger than the ones you've got, you start again
with a smaller streamer length :)

Steve C.