RE: DRSSTC Primary Circuit Feedback Control

["Tesla list" <tesla@xxxxxxxxxx>]

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

Terry,

I am a believer in primary current feedback. I've used it on one coil with
success and I plan to use it for my next DRSSTC too. I found that secondary
current feedback doesn't always give exact zero current switching, because
streamer loading screws up the phase relationship between primary and
secondary currents. In experiments I did on a SGTC converted to DRSSTC
operation, close-in ground strikes made the phase shift between the two
currents jump through 180'.

This phase shift effect is less dramatic in tight coupled coils which is
probably why Steve and Dan get away with it.

>There are three situations where the switching is naturally
>soft: Drive at one of the resonances (that produces increasing input
>current and slow ringup), and drive exactly between the resonances,
>that procuces the fastest possible ringup, with proper dimensioning.

"Drive at one of the resonances" is what Steve Ward does and "drive exactly
between the resonances" is what Jimmy H. designed his system to do. (So I
assume he used "proper dimensioning") But when Jimmy tuned the system
empirically for maximum spark length he found that he was running at one of
the resonances. So I concluded that there is no real advantage to running
between the resonances, even if it is theoretically "optimal", and I
abandoned this line of inquiry. Unless someone can persuade me to reopen it
;)


Steve C.