RE: SSTC, Modes and soft switching

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

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

On 23 Aug 2004, at 7:41, Tesla list wrote:

 > 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.

Referring to point 3., I suspect without proof that the lower-than-
sparkgap optimum tuning may be a result of the lower primary losses.
I would be interested to know whether the final frequency came close
to matching the LSB condition I mentioned earlier.

Malcolm