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Registered Member #1906
Joined: Sat Jan 03 2009, 05:06PM
Location:
Posts: 39
Would there be any problems with charging capacitors and discharging them in parallel? except for the switches being complicated.
I read somewhere, probably on this forum, that the capacitors might charge differently and when reconnecting them in series this might damage them, is this correct?
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Try a google search for "Marx Generator". It is a simple device that utilizes a series of spark gaps to do exactly what you are talking about: charge capacitors in parallel and discharge in series.
The problem with charging capacitors in series (what you have probably heard about) is that they may have slightly different capacitances which will cause the voltage to be unevenly distributed among the caps. Some could be subjected to overvoltage while others are not charged fully.
This is usually applied to electrolytic caps since they often have capacitances that vary greatly from the label. The solution to the problem can be as simple as placing "balancing resistors" across each capacitor.
Registered Member #90
Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301
A balancing resistor is slightly lame since it wastes energy by leaking current. Your idea to charge in parallel is better (except for all the switches, as you note). The series arrangement offers the advantage of discharging a much higher voltage than your power supply can provide.
This has been done before in the Discovery Channel 7KJ coilgun. Scroll down to the "charging system" and make note of banks of relays that are timed by an industrial controller module.
They even used another relay for two-speed charging. To avoid overloading the power supply they start charging from zero with a higher series resistance, then drop to a lower resistance when the capacitors are half full.
Cheers, Barry Twitter has conclusively proven that noone really needs things like adverbs, punctuation, or non-abbreviated words. Fairly obvious observations – such as this one – are pointless as well, which means that this entire sentence is superfluous. As is this one. And this one. And this.
Registered Member #1617
Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139
The marx generator circuit connects the caps in parrallel via a high value resistance or inductance, so to the discharge pulse (which has alot of high frequency components), the parrallel connection looks like an open circuit (or at least a relativley high impedance), you would have to either have some sort of passive netowrk like this or a set of switches etc to disconnect the parrallel conections before connecting them in series.
Registered Member #1906
Joined: Sat Jan 03 2009, 05:06PM
Location:
Posts: 39
Thanks. Thats probably all i wanted to know, unless you happen know of some nice design of this kind of switch. In that case I'm quite curious to see what it looks like :P
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Capacitor charging in parallels & discharging in series
