Just wondering about DRSSTC coils... almost all the coils I have seen on
the net use a break out point for the sparks to jump off...
Why is that?
The secondary resonance frequency changes quite a bit due to the
arc capacitance. There is a choice of either being well in tune for
small or large arcs. Preferably the coil is in tune for the large arcs,
since that is when power is needed most.
So initially, before breakout, you need a lot of primary current to
get enough secondary voltage to cause breakout, since the coil is
out of tune then.A breakout point enhances early breakout and so
reduces primary current requirements.
most of our shows entail that we stand ON the coil so the sparks jump
FROM us.
The coil is obviously tuned to allow for the top load of the person
standing on it, however when moving around up there, the coil does go in
and out of tune a bit as a result...
Would a DRSSTC with secondary base feedback, compensate for this level
of frequency shift?
Or would it all go terribly wrong...?
Yes, it might. The phase between secondary and primary current depends
much on the tuning, though. You'll not be switching the IGBTs at the time
of zero current, which puts a considerable burden on them. Primary feedback
allows for that. I'd go for primary feedback, since you'll likely have a
huge top capacitance anyway, where the movements of the person on top
won't change much in relation.
Udo
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