In [1]:
Vbat = 200 #V
Imotor = 2 #A
Lm = 50e-6 #H

frequency = 20000 #Hz
tcycle = 1.0/frequency

Iripple = Vbat / Lm * tcycle/4
Vripple = 0.2 #V

C=1/64*Vbat/Vripple/Lm*tcycle**2

print Iripple


0.5