RE: DRSSTC driver tests- Dual resonance disaster

["Tesla list" <tesla@xxxxxxxxxx>]

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

>These values, 200 Ohms and 52 nF, look quite strange for streamer load.

Well the reason is that I am using a fake "secondary" with the same number
of turns as the primary, and resonated with the same size of capacitor as
the tank capacitor. It's safer and more convenient than a real Tesla
resonator for prototyping. If it were a real resonator this would correspond
to about 220k in series with 15pF.


>So, feedback can´t be from the input current. Can be from the output
>voltage, or from the secondary current, with a 90 degrees phase shift.

Well I think feedback from the input current has its advantages. The reason
is that I don't trust the secondary current to always be exactly in
quadrature with the primary current. I have seen the phase shift change with
secondary loading and detuning, sometimes flipping through 180', and I think
this is a major cause of poor performance and unreliability.

As long as breakout always happens before the first "notch" and loads the
coil heavily enough to stop reversal, primary current feedback should be
safe. Or, I think the reversal could be got rid of by deliberately mistuning
one of the resonators or skewing the drive frequency to one side of centre.


>Look at these simulated waveforms (mode 17:19:21...

Does this mean that the lower and upper split frequencies of the resonators
are 17:21 and the drive frequency is 19? Also can your software simulate
self-resonant tunings (which I guess would be represented by say 17:17:21 or
17:21:21 in your example)

On a similar note, I have been trying to derive an equation for the steady
state transimpedance (ie Iin=f(Vin, Vout, L1, L2, C1, C2, k, omega) where
Iin, Vin, Vout are complex quantities) I want to know this because it would
let you predict the worst case primary current in a self resonant coil,
knowing the breakout voltage and the coil constants, and adding the boundary
condition that Iin and Vin are in phase.

I know that several of the transfer functions are ill defined at the poles
for a system with no loss resistance (for instance vout/vin tends to
infinity, Iin/Vin tends to infinity) but I believe Vout/Iin should tend to a
constant at the poles. My reasoning is that Vout and Iin both tend to
infinity, and infinity divided by infinity could perhaps be a finite number
;)

If you (or anyone else) have the transfer function for the dual resonator in
pole-zero form I'd be very interested to see it. I tried deriving it myself
but it's a long time since I've been in a maths class :-(


Steve C.