Re: Voltage Reversal of Pulse Caps

Re: "Voltage reversals"
	I think there are two ways in which rapid reversals can
affect the life of the capacitors.  The first is in resistive
loss due to current flowing.  The current will be proportional
to the rate of discharge, which is negligible during charging 
from the line (way under an amp, and only 120 times per second or
so) but very great during dicharge through the gap and primary
winding.  This effect is due to heating.
	A second failure mode would be if there is any residual
air in the capacitor.  It will (or at least can) become ionized
and eventually will break down the surrounding insulation.  A
number of years ago I was involved in a radar project where we
were cathode pulsing a klystron at 35 k

!-at-#$% line feed!

35 kV.  The pulse forming network used a bunch of 600 mmfd mica
capacitors of home-grown (Hughes Aircraft) construction, and we
had a great deal of trouble with breakdown due to internal corona
effects before the potting procedure was worked out.  In this 
case the pulse rate was of the order of 15,000 per second and the
lifetime was in the tens to hundreds of hours initially.  I
assume the capacitors we are getting are much more conservatively
rated, as size is not the same constraint it was in this application.
	One last point.  Not sure what you mean by "forcing the
energy into the capacitor", but ALL of the energy in the discharge
is put into the capacitor during charging from the transformer.
Still waiting for the capacitors eagerly, even though I don't
have a transformer or coil big enough to use them yet.
Best wishes,
Ed Phillips