RE: SSTC theory (scope shots)

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

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 1 Jul 2004, at 16:17, Tesla list wrote:

 > Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com>
 >
 >  >In some respects this is really disappointing because it means that
 >  >current is ramping up in the primary as well as the secondary does
 >  it >not?
 >
 > Yes, this is exactly what happens. The energy in the primary circuit
 > (1/2*Lp*Ip^2, or 1/2*Cp*Vp^2) ends up roughly equal to the energy in
 > the secondary circuit.
 >
 > There are two differences though:
 >
 > 1: The energy in the primary mostly empties into the secondary after
 > the inverter shuts down. If we are cynical and say that half of it
 > goes to the secondary and the other half returns to the DC link, then
 > we are still achieving a bang energy 1.5 times greater than a
 > conventional coil with the same primary component ratings.

Right. I also noted that there was no phase reversal present in the
oscillogram of the secondary.

 > 2: If the system runs in the quasi-CW mode, where the top voltage is
 > heavily clamped by breakout, the primary voltage and current will
 > level off. Therefore, the energy in the primary and secondary circuits
 > is no longer increasing, however the energy transferred to the
 > discharge is still increasing.
 >
 > This allows for an almost unlimited effective "bang energy" by just
 > increasing the inverter on-time, even though the voltage/current
 > ratings of the primary and secondary are modest.

Sure.

 > You can also imagine that it would allow the creation of sparks that
 > were long compared to the length of the resonator, without flashover,
 > and indeed Steve Ward's ISSTCs (and some built by others) do behave
 > like this.
 >
 > It seems that the way to promote this quasi-CW operation is to use
 > tight coupling (k=0.3)

The primary ringing up like that will be a function of loose coupling
- i.e. energy is not transferred to the secondary as fast as it is
being delivered to the primary. I figured that would be the case
anyway but was still surprised to see the beating. I'm not surprised
any more considering the relatively low coupling constant. Obviously,
the tighter the coupling the better but I realize that only so much
is practicable. On the plus side though, it would still seem that the
primary L/C ratio can be usefully boosted to keep primary (and
device) currents down while recognizing that voltages across the caps
and coil would climb significantly.

Malcolm