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RE:Wiring caps in series
>> A little while ago, somebody on this list asked if it would be
>>practical to make a high voltage capacitor by wiring a bunch of
>>photo flash (330 V 160 uF) caps in series. I never saw an
>>answer to this question.
>>As an experiment, I tried wiring 6 of them in series and then
>>running them through several charge/discharge cycles of 1500
>>volts - by putting 1500 volts between points A and G (see
>>"schematic" below), and then bridging points A and G with a
>>heavy wire (BANG!!!).
>> || || || || || || o-||--||--||--||--||--||--o ||
>> || || || || ||
>> A B C D E F G
>>The first time I charged them up, each of the caps had about
>>the same voltage across them (Vab=Vbc=Vcd=Vde=Vef=Vfg=250
>>volts). After dischaging them by bridging A and G with a wire,
>>I assumed that all of the caps would have discharged to some
>>low value. What I found instead is that the caps had more or
>>less random voltages on them (between -50 and +50 volts).
>>Charging the set up again (by putting 1500 volts across points
>>A and G) resulted in widely varying voltages across the various
>>capacitors.
>>Given this situation, I could easily see some of the caps
>>failing due to over-voltage conditions, which are caused by the
>>varying voltages that result when the capacitors are charged
>>and discharged in series.
>>What did I do wrong in my experiment?
This is very typical with wiring caps in series. In the old days, we used to add
a resistor across each cap. Select the resistors to evenly distribute the
voltage, also, select resistors of high resistance and proper power rating. Note
that this addition has a side effect of changing the impedance of the circuit.
Ric