# Confused while designing copper busbars

Hello Guys!

I was designing copper bus-bars which can withstand 1 kA current. Actually I am going to discharge a several DC capacitors into those bars. So, I was confused in the dimensioning the cross section. Is 25mm * 3mm cross section enough? I have made my calculation using 1.6 A/mm2 current density for copper. Help is badly needed.
Thanks in advance. It is straight forward to calculate the voltage (IR) drop in the copper. Is this too high for your application?

Does the copper resistance appreciably change the RC time constant of your pulse?

If the voltage drop is acceptable, what is the heating in the conductor for a single capacitor discharge? because the instantaneous heating is proportional to I2R, and the capacitor discharge current waveform I(t) is exponential, the joule heating is equal to ∫I2(t)·R·dt.

Using the specific heat for copper (0.390 joules per gram per degree C), what is the temperature rise for a single capacitor pulse?

Bob S

dlgoff
Gold Member
This reminds me of the time that I designed some buss bars used the a temperature "burn-in" chamber form a bunch of avionic navigation radios. Needless to say, thermal expansion is a big consideration.

Voltage drop is negligible, RC constant is not affected as it has very negligible resistance. Question remains is, for a rough estimate, how much cross-sectional area does it require to withstand 800A-1000A for duration of max. 3 or 4 seconds, voltages being 200/250 at 50 Hz. Thanks for your response. (I must tell, I am going to adjust the RC constant of whole setup using a rheostat and will make it near around 2-3 or max. 4 seconds if necessary. My setup will work if i reach 2 seconds.)

For rough calculation of temperature rise of copper,
calculate the energy stored in the capacitor,
then using this energy calculate the temperature rise of the copper.