Utilization of Electrical Energy

A 230V, 25kW d.c. shunt motor running at its rated speed of 1500 rpm is to be braked by reverse current braking. The armature resistance is 0.1 ohm and the rated efficiency of the motor is 88 percent. Calculate (i) the resistance to be connected in series with the armature to limit the initial braking current to twice the rated current, (ii) the initial braking torque and (iii) the torque when the speed of the motor falls to 600 rpm.