. The speed of an 8 kW, 220V, 1250 rpm separately-excited d.c. motor is controlled by a single-phase full converter. The rated armature current is 30 A. The armature resistance is Ra = 0.25 Ω and armature inductance is La = 15 mH. The a.c. supply voltage is 300 V. The motor voltage constant is Ke φ = 0.20 V/rpm. Assume that motor current is continuous and ripple free. For firing angle α = 60˚ and rated motor current, determine: a) Speed of the motor [637.5 rpm] b) The input power to the motor [4050 W] c) How to increase the speed to 1000rpm [Ans : (a), (b