Sizing a power supply smoothing capacitor

[Monte]

My numbers for a 41 vdc power supply

3 axis @ 4.2 amps/ motor = 12.6 total possible motor amps

12.6 * 0.667 = 8.4 amps for 2/3's minimum power supply rating

14*2*1.414 = 39.6 I have (2) 14v transformsers that I'll series together, 39.5 is close enough

80,000*8.4/39.5 = 17013uF
I have a 20,000uF 50vdc cap, is that close enough? How close up or down do the capacitors need to be to the calculated value?

Thanks,
Monte

[smarbaga]

hello
your calcs. looks good.
a rule of thumb :
2000 uf per amp.

[vger]

Only problem I see is with the voltage rating. With 40 volts RMS you get about 56 volts peak, enough to damage a 50 volt cap. Many electronics manufacturers will approximately double rate the voltage of capacitors. If the voltage in the system is 56 volts they would use a 100 volt cap.

Steve