A DC chopper is used for regenerative braking of a separately excited DC motor. The DC supply voltage is 400V. The armature current during regenerative braking is kept constant at 300 A with negligible ripple. For a duty cycle of 60% the power return to the DC supply is
(a) 78 kW (b) 58 kW (c) 38 kW (d) 48 kW
(a) 78 kW (b) 58 kW (c) 38 kW (d) 48 kW