RE: More ISSTC theory stuff (l o n g)

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

>The result is curious, and maybe very significant:
>If only the load resistance changes, the input impedance -remains
>resistive-,
>and changes to match the load. This happens because of the doubly tuned
>transformer, that operates independently of the load.
>I verified then what happens if the capacitive loading changes, due to
>streamer growth. The result is not very good: The input current
>-increases-
>and becomes reactive

eep!

But did you do this simulation assuming a fixed frequency drive, at the
unloaded resonant frequency? We are now using self-resonant and PLL drive
circuits that adjust the inverter frequency to keep the primary current in
phase with the voltage. The reason being that our IGBTs like zero-current
turn-off.

I _think_ that with one of these drive circuits, the reactive component
would just be forced to go away. Unless the circuit was in a state such that
there was _no_ frequency at which the input impedance was purely resistive,
in which case I have no idea what would happen, but it would probably be
spectacular and expensive.

I mentioned the L-match thing to Richie Burnett and he tried base-feeding a
resonator straight from the inverter, through a L-match network. His setup
is like an ISSTC in that it shows the desirable dual resonant behaviour (no
"magnetizing current") but also like one of your directly-coupled spark-gap
coils in that the voltage gain n=1. However it seems to perform just as well
as an ordinary SSTC.

I think the inductively coupled ISSTC might still have the advantage for
high powered coils though, since it has an extra untuned transformer (n) to
help with the impedance matching, thus the primary "L-match" can have a
lower loaded Q and hence lower losses.

>I get: In 200 us: 2.4 J

whoops, it looks like I missed out a 1/sqrt(2)

Steve C.

```