Answer Happy

B2. (a) What would be the effect of armature reaction on D.C. machines? (4 marks) Suggest one method of reducing armature reaction on operation. (b) The armature resistance and field resistance of a shunt D.C. motor are 0.15 2 and 105 2 respectively. The motor is connected to the supply voltage of 240 V D.C. and draws an armature current of 240 A at a torque of 200 Nm. If the rotational power loss is 1 kW, evaluate (i) the back e.m.f., (ii) the motor speed in rev/min, (iii) the total losses of the motor, (iv) the input power of the motor, (v) the efficiency of the motor, and (vi) the motor speed in rev/min at one-third torque. (2 marks) (3 marks) (4 marks) (2 marks) (2 marks) (3 marks)