Re: Voltage Reversal of Pulse Caps

Hi Malcom,

>Regarding reversals, When you discharge
>the capacitor into the primary coil, it firstly discharges to zero
>volts and then swings on through to end up with some voltage across
>it of polarity opposite to that which it originally had. This voltage
>is somewhat less than it started out with because the magnetic field 
>generated is shared between the two coils, both of which end up with
>a proportion of the original cap energy.  .....................
>.......................Note that these reversals are
>occurring at the resonant frequency i.e. 10's/100's of thousands of
>times per second.

Yes, that is true.  But the reversals which affect the life of the capacitor to
any great degree are those of when the capacitor is pulsed.  The only time this
ocurrs is when the transformer charges it across the gap. The amount of energy
(Joules) at this time is very high.   And besides, have you ever figured out the
time constants of capacitor charging at the primary voltage at thefrequency of
operation.  I haven't, but I will bet you there is not much energy (Joules) able
to get into the cap when polarity reverses at the frequency of resonation.   I
don't believe the ringing reversals can force near the amount of energy into the
capacitor as the pulses.  If it did, a single pulse wound make the primary ring
for several seconds (Wouldn't that be wonderful!).  What really slowly "wears
out" the capacitor is the pulsing from the gaps at the time of polarity reversal
of the input frequency.

Scott Myers