A 220 V unsaturated shunt motor has an armature resistance (including brushes and interpoles) of 0.04 W and the field resistance of 100 Ω. Find
(a) the value of resistance to be added to the field circuit to increase the speed from 1200 to 1600 rpm, when the supply current is 200 A,
(b) With the field resistance as in
(a), find the speed when the supply current is 120 A. If the machine is run as a generator to give 200 A at 220 V, find
(b) the field current at 1300 rpm, and (d) the speed when the field current is 2 A.