Al. A DC series motor with armature resistance (Ra) of 0.60 is connected across 220V supply source. It is used to drive a load. The motor torque is proportional to the square of motor speed (T x N). When the speed (N1) is 650rpm, the armature current (Iai) is 32A. A resistor of resistance 2Q is now inserted in series with the armature circuit in order to decrease the motor speed to 450rpm. (a) Calculate the new armature current (Ia2). (b) Calculate the new induced emf of armature (E2). (3 marks) (2 marks) A2. A three-phase induction motor has 4 poles. It has the following specification at rated conditions as indicated on the motor name plate. Output power: 11kW Input line voltage: 380V Input line current: 25A Field winding connection: Delta Frequency: 50HZ Speed: 1420rpm Power factor: 0.75 Determine: (a) the efficiency of motor; (b) the slip of motor. (2 marks) (3 marks)