Zapp's phase shift correct will not work. Yes, like smoke and mirrors it
works in the circuit he has, but when he hooks it up to a real TC load it
is
not going to work properly.
Zero crossing under a load can be achieved as long as there is not change
--- no change in potential or no change in current. What may look like
perfect zero crossing at full load may cause very high current switching
before you get to the full power level. This is not shown on the video
because no load is connected. When a real load is connected the
currents will definitely dynamically change.
With no load applied and just adjusting the firing angle of the gate
drives,
you can absolutely set perfect zero crossing. When the load is
dynamically
applied there is a slight shift in phase angle because the inductance
changes due to the current changes --- which are very rapid and dynamic.
The overshoot he is trying to null out is not a zero cross over problem.
Overshoot, which is very high in his waveforms, and which he is trying to
null out, is caused by improper turns ratios on the gate drive
transformers. This is where the overshoot problem is occuring, not from
the
phase angle.
If you watch the you tube video you will see the amplitude change and
there
is no change in phase shift. You need to adjust and perfectly match your
gate drive transformers to correct this problem.
The only way to make it work is dynamically follow the rapidly changing
load
perhaps with a microprocessor. This would be a step in the right
direction
to solving this problem which tends to amplify itself as coils get larger
and the power levels increase. There is no simple, easy solution. It can
only be solved in a dynamic fashion accurately tracking the currents.
Dr. Resonance
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