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banned on 5/26/2009 Registered Member #1877
Joined: Mon Dec 22 2008, 02:03AM
Location:
Posts: 147
I have a 1.312 kj capacitor bank, it is 500 volts at 10500 uf. ive been discharging it into a coil recently when i found out about the reverse voltage back into the capacitor bank. sure enough, i measure -100volts on the capacitor bank after discharge! so, i sampled a few diodes from stmicroelectronics, i have 9. they are 1000v @ 60a each. how should i go about hooking them up? i would need a resistor correct? what size of resister? where can i get one? any help is greatly appreciated.
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
I think the resistance put in series with the diode should be large enough to keep the peak current under the peak current of the diode (it's more than 60A). Stick the diodes across the cap rails so that the cathode goes on the positive rail and the anode goes on the negative rail. I don't think some people use resistors though.
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
I don't use resistors on my current 600J CG but my two diodes add up to a "pulse" rating of over 2kA.
The peak current is sometimes listed as something like 8ms on the datasheet and assumes many things. Look at the current limit graph on the specsheet for the pulse length you are expecting. I would try to get diodes that are rated such that you don't need resistors, but getting ultra fast diodes can sometimes make this impossible/impractical.
banned on 5/26/2009 Registered Member #1877
Joined: Mon Dec 22 2008, 02:03AM
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Posts: 147
would the capacitors be damaged by now? i have discharged them into a coil without protection about 10 times now. is there any way to reverse damage to electrolytic capacitors?
banned on 5/26/2009 Registered Member #1877
Joined: Mon Dec 22 2008, 02:03AM
Location:
Posts: 147
i measured -100v only once. be, again, is there any way to reverse the damage? im thinking like memory on batteries, they lose their ability to store their charge if you keep charging them, but i don't think its the same concept. but any ideas?
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Diodes in anti-parallel
