RE: SSTC, Modes and soft switching

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

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

Hi all,

Here is a little view from the lab on the mode-splitting and tuning
properties of DRSSTCs. Well my DRSSTC at least.. I'm not sure how it applies
to systems with higher coupling and lower primary surge impedance.


1. It looks like it is possible to get soft switching all the way through a
burst, no matter what the tuning and coupling of your DRSSTC. You use a
phase locked loop or self-resonant driver circuit, sensing the primary
current, to force the phase angle betwen inverter voltage and primary
current to zero. The system then operates at a frequency where this phase
condition holds true.

2. With a driver like this, that forces zero phase shift, you then have to
tune your primary to find the point of maximum primary current. This also
seems to be the point of highest output voltage, and largest and fiercest
sparks :)

3. When I checked my coil with a frequency sweep after tuning it like this,
I found the primary was tuned surprisingly low (lower than the optimum
tuning when I used the same coil with spark-gap excitation) and the lower
mode was emphasized compared to the upper one.


Steve C.