A starter is to be designed for a 10 kW, 250 V shunt motor. The armature resistance is 0.15 Ω. This motor is to be started with a resistance in the armature circuit so that during the starting period the armature current does not exceed 200% of the rated value or fall below the rated value. That is, the machine is to start with 200% of armature current and as soon as the current falls to the rated value, sufficient series resistance is to be cut out to restore current to 200% (or less in the last step).
(a) Calculate the total resistance of the starter.
(b) Also calculate the resistance to be cut out in each step in the starting operation.