A 1-kW, 85-V, permanent-magnet dc motor is to be driven from a full-wave, phase-controlled bridge such as is shown in Figure. When operating at its rated voltage, the dc-motor has a no load speed of 1725 r/min and an armature resistance Ra = 0.82?. A large inductor (L = 580 mH) with resistance RL = 0.39? has been inserted in series with the output of the rectifier bridge to reduce the ripple current applied to the motor. The source voltage is a 115-V rms, 60-Hz sinusoid. With the motor operating at a speed of 1650 r/min, the motor current is measured to be 7.6 A.

a. Calculate the motor input power.

b. Calculate the firing delay angle ?d of the SCR Bridge.

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