1. A DC shunt motor, with supply voltage of 220V which rotates at 1000rpm for driving...

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1. A DC shunt motor, with supply voltage of 220V which rotates at 1000rpm for driving a mechanical load. The armature current through the rotor is 20A. Armature resistance is 0.32. a) Calculate the induced emf (E1) in the armature. 6 marks In order to increase the speed to 1250rpm, the motor is now under flux control. The flux is decreased to 75% of its original setting. b) Calculate the new induced emf (E2) in the armature. 8 marks c) Calculate the new armature current (a2). 6 marks d) Calculate the power input (Pin) to the armature with the new armature 5 marks current (Ia2). 2. A400V three phase 60HZ induction motor with 4 poles rotates at 1620rpm with a usable output torque of 400Nm. The mechanical loss for friction and windage is 100Nm. Calculate: a) the synchronous speed (Ns) in rpm. 4 marks b) the slip (S) at full load output. 4 marks c) the frequency of induced emf (f) of rotor circuit in Hz. 4 marks d) the usable mechanical power output in W. 3 marks e) the gross mechanical power output in Ww. 6 marks f) the rotor copper loss in W. 4 marks 1. A DC shunt motor, with supply voltage of 220V which rotates at 1000rpm for driving a mechanical load. The armature current through the rotor is 20A. Armature resistance is 0.32. a) Calculate the induced emf (E1) in the armature. 6 marks In order to increase the speed to 1250rpm, the motor is now under flux control. The flux is decreased to 75% of its original setting. b) Calculate the new induced emf (E2) in the armature. 8 marks c) Calculate the new armature current (a2). 6 marks d) Calculate the power input (Pin) to the armature with the new armature 5 marks current (Ia2). 2. A400V three phase 60HZ induction motor with 4 poles rotates at 1620rpm with a usable output torque of 400Nm. The mechanical loss for friction and windage is 100Nm. Calculate: a) the synchronous speed (Ns) in rpm. 4 marks b) the slip (S) at full load output. 4 marks c) the frequency of induced emf (f) of rotor circuit in Hz. 4 marks d) the usable mechanical power output in W. 3 marks e) the gross mechanical power output in Ww. 6 marks f) the rotor copper loss in W. 4 marks