A 25 hp, 500 V, 1200 rpm separately excited DC motor is controlled by a three-phase full-converter. The field current is

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A 25 hp, 500 V, 1200 rpm separately excited DC motor is
controlled by a three-phase full-converter. The field current is
also controlled by a three-phase full-converter. The AC input to
armature and field converters is three-phase, Y-connected, 208 V-60
Hz. The armature resistance is Ra = 0.1 ohms, the field circuit
resistance is Rf = 140 ohms, and the motor voltage constant is Kv =
1.1 V/A rads-1. Electrical, viscous friction and no-load losses are
negligible. The armature and field currents are continuous and
ripple free. The field circuit converter is set to the maximum
field current, the developed torque is Td = 120 N-m and the delay
angle of the armature converter is 0 deg. The input power factor
would be equal to:
a.
0.61 lagging
b.
0.78 lagging
c.
0.95 lagging
d.
0.95 leading