Calculating Max Discharge Current for Nichicon QR 450V 0.012F Capacitors and SCR Rating

I was wondering if there is a formula to find the maximum amperage put out by a capacitor because I need to find ratings for an SCR and wire gauge for and experiment I am conducting. I will be using one 0.24 farad 450v bank without an SCR (as this bank needs no switch) and one 0.024 farad 450 volt bank with an SCR. The capacitors are Nichicon QR screw type 450v 0.012 farad capacitors for rapid charging and discharging. I'm also wondering if either bank would need cooling?

Hi,

Maybe this Online Calculator can help.

Thank you for the help, I would prefer a formula that I can remember instead of a calculator that doesn't really work.

IMHO it depends on the system inductance.

See: http://www.elginindustries.com/~/media/GES Tech docs/GES Capacitor Inrush Current Calculations.ashx

This is one dangerous experiment, the energy involved is quite high(C*v*v Joules). The potential to have molten copper flying around, or ruptured capacitors, is high, so wear safety glasses. On no account put a short on the system!
Put a discharge system in place to bring the capacitors down to a safe voltage before you start diving in to make any changes.
What load are you discharging the capacitors into, this and the impedance of the connecting wire, and capacitors will determine how quickly you can cycle the system.
I am assuming here that the capacitors are rated for something more than you require of them.
The standard formula i=C(dV/dt) applies to this or any other systems involving capacitors. You can arrange the formula to suit the known values.
Thermal management will improve the lifetime of the capacitors, if this is a short term experiment, it probably won't matter. The large can size will mean that transferring heat from the core is a problem.
Read this document,

http://www.digikey.co.nz/Web%20Export/Supplie...8/PDF/CDE_PredictingLifeTemp.pdf?redirected=1

it probably covers a lot of what you need to know.

cheers,
Richard

I will be carging the capacitors to the 450v that they are rated to unless it wouldn't be advised. The capacitor's tolerance is +20 and - 20%. I will be making attaching a railgun to the larger bank (caps straight to rails, no switch will be needed). The smaller bank would go to a coil of magnet wire. Also, what would you advise for a discharge system? Would it be advisable to wire the banks in series or parallel? I will probably put them in series.