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Registered Member #61406
Joined: Thu Jan 05 2017, 11:31PM
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Posts: 268
I've got these caps that are 2.2nF and 15kv with a discharge of 2000v/1us,using the formula i=C*V/it works out to 4.4amps. I was wondering if having them in series say eight they will still supply 4.4amps,and what will happen if they are in parrellel. I'm after 90kv working voltage, 120kv Max, with a high amp discharge, what caps would you recommend. thanks
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727
I was wondering if having them in series say eight they will still supply 4.4amps,and what will happen if they are in parrellel.
Capacitors will supply more than 4.4A, but they will degrade. 4.4A is a repetetive capability for long time reliability. Depending on what you want to try you can ignore this current limitation within reasonable limits. I dont know what type of capacitor you have, but if its a foil capcitor, the individual metal layers will disconnect over time. Anyway: a series string of those capacitors would technically still have this current limit since in a series connection the current is equal through all elements, so the current limit of the weakest element applies. A parallel connection will increase your current capability. Your capacitor can only hold 0.25J of energy. Its strage, but my gut feeling would be that this energy couldnt damage the capacitor in a one-time pulse even if you directly short the terminals. (arcing neglected, of course) But i could be totally wrong ^_^
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
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I saw a similar issue with back-emf noise from a switching power supply punching though China sourced ceramic caps. In basic theory, the higher ESR should slow down the discharge in series, but if each cap's loading is unbalanced than a similar failure mode will eventually occur as any of the individual component in the chain ratings are exceeded. Thus, for some cap types a cascade failure can occur as each element in the chain causes the next weakest component to successively fail.
The output impedance in parallel tends to balance the load across the caps, but in a pulse mode these can still create RF shorts due wide spectrum combing. YMMV depending on the dialectic temperature ratings.
Maybe there is some kind of step-recovery-diode out there that will give you the signal you want.
Registered Member #61406
Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268
Hen918, thanks for the link, I don't think my experience is good enough for 2kJ? Deralbi, the capacitor is ceramic, thinking at the moment 6*6 array, at eight dollars each. carbon rod, I don't know what a step recovery diode is, I'm thinking of high amp arcs, with a shortish time frame With the power supply I can't add balance resistors, not enough current.
The caps are on mouser starting at $9.5 Thanks all
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Pulse discharge of capacitor, series and parrellel
