3. (20%) The dc machine (12kW, 100V, 1000 rpm) is connected to a 100V dc supply...

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3. (20%) The dc machine (12kW, 100V, 1000 rpm) is connected to a 100V dc supply and is operated as a dc shunt motor. At no-load condition, the motor runs at 1000 rpm and the armature takes 6 amperes. Data for the magnetization curve at 1000 rpm are (A) 0.05 Ea(v) 11.4 0.18 0.21 22.4 33.4 0.62 0.55 0.38 0.28 77.4 66.4 55.4 44.4 0.75 0.99 88.4 1.3 99.4 110.4 (a) Find the value of the resistance of the shunt field control rheostat (Rfc). (5%) (b) Find the rotational losses at 1000 rpm. (5%) (c) Find the speed, electromagnetic torque, and efficiency of the motor when rated current flows in the armature. Consider that the air gap flux remains the same as that at no load. (10%) 3. (20%) The dc machine (12kW, 100V, 1000 rpm) is connected to a 100V dc supply and is operated as a dc shunt motor. At no-load condition, the motor runs at 1000 rpm and the armature takes 6 amperes. Data for the magnetization curve at 1000 rpm are (A) 0.05 Ea(v) 11.4 0.18 0.21 22.4 33.4 0.62 0.55 0.38 0.28 77.4 66.4 55.4 44.4 0.75 0.99 88.4 1.3 99.4 110.4 (a) Find the value of the resistance of the shunt field control rheostat (Rfc). (5%) (b) Find the rotational losses at 1000 rpm. (5%) (c) Find the speed, electromagnetic torque, and efficiency of the motor when rated current flows in the armature. Consider that the air gap flux remains the same as that at no load. (10%)