Richards, Justin P wrote:
>
> Yes, you are correct.  I had not considered that current was going to
> flow in the opposite direction.  The drawing I made sort of obscured
> this.  I can think of a way to eliminate this but then the uneven demand
> placed on the batteries would be increased and as suggested present more
> problems than it has solved.


You suggested using 400v fets, that won't work.
You have +340v dc and -340v dc supplies, essentially,
switching into a +/- 340v peak wave. The max fet volts
will be +340v to -340v. You need *at least* 680v
insulated fets.

Now look at typical HV switcher, like a TV h-output
stage. Normally about 110v dc regulated input, at
about 100W or about 1A. This will use a 1500v 6A
MINIMUM rated switching transistor. To switch a
100v rail! And they are still somewhat unreliable,
even with snubbers and damping all over the place
keeping the max volts down. Continually switching
large voltages is very hard on semis. It will be
cheaper and more reliable on the semis to switch
100A at 36v than to switch 10A at over 300 volts.
Sorry! :o)
-Roman

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