(a) A shunt dc motor has a rated armature current of 20 A , rated
(10 marks) field current of 0.5 A , rated voltage of 25 V and maximum rotational speed of 750 rpm . When the rotor is locked, an armature voltage of 1.02 V produces 17 A of current flowing in the armature; while a field voltage of 25 V produces a field current flow of 0.5 A . At no load, with the terminal voltage applied is 24 V , the motor speed is 750 rpm and the current drawn by the motor is 1.32 A . The brush voltage drop is estimated to be 2 V in all conditions. The stray loss is estimated to be \( 1 \% \) of the input power. Determine the output power produced by this motor and the efficiency at the rated conditions.