DieselShip's Online Content Library

Q7. A. What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance.

b) An 8kw, 230V, 1200 rpm d.c shunt motor has Ra = 0.7W. The field current is adjusted until, on no-load with a supply of 250V, the motor runs at 1250 rpm and draws armature current of 1.6 amps. A load torque is then applied to the motor shaft which causes la to raise to 40 A and the speed falls to 1150 rpm. Determine the reduction in the flux per pole due to the armature reaction.