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damages when charging capacitor?

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coolgod

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I have a couple of 100v 10000 uf capacitors used for a coilgun. I need a 100v powersupply charger but i can't get the voltage to be at 100, it's usually about 105ish, if i use 105v to charge the capacitor but stop charging at 98 ish does it damage the capacitor on the inside? Sorry I am new to these things, thank you
 

coolgod,

I have a couple of 100v 10000 uf capacitors used for a coilgun. I need a 100v powersupply charger but i can't get the voltage to be at 100, it's usually about 105ish, if i use 105v to charge the capacitor but stop charging at 98 ish does it damage the capacitor on the inside?

Well made caps have a safety margin for voltage. The more you go over the rating, the closer you get to falling off the cliff. I would think that going 5 volts over the 100 volt rating is not too bad. Not energizing the cap to its full rated voltage lessens the stress on the dielectric, so that is fine. Be careful, energizing a 10000 µf cap to 100 volts stores 50 joules of energy, along with plenty of volts to send it through your body. If that happens, you will be a hotgod.

Ratch
 

i was thinking maybe a voltage divider to change the voltage? I need my coilgun to be consistent thus i need the voltage in the capacitor to be the same each time.
I'm currently using a transformer that is suppose to drop ac main 118-120v ish to 108-110v. That is connected to a bridge rectifier which converts it to ac. I need my coilgun to be precise and charging to be not too slow. I'm thinking if i use diodes and ac main voltage flucates my coilgun will be affected. I have 3 35w rheostat, do you think it's possible for me to hook that up and fine tune the voltage to be 95-100v ish?
I'm worried about the rheostat heating up, do i need a load or limit resistance on both circuits coming out of the rheostat? I've actually melted one b4, it was glowing bright red.
Another general question about capacitors, i see my capacitors after charging to 100v starts self discharge itself pretty quick usually down to 84v ish in under a minute, then it drops very slowly. Is this a sign of old capacitors? Should I reform them to fix this issue?
 

coolgod,

i was thinking maybe a voltage divider to change the voltage? I need my coilgun to be consistent thus i need the voltage in the capacitor to be the same each time.

It appears to me that if you want consistency, you should be looking at an automatic voltage regulator.

Ratch
 

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