Power Electronics - Engineering

Q1:

A dc separately excited motor has constant field current. The armature is fed from a single phase supply through a full converter. When a = 0, speed is 500 rpm. If a = 45°, the speed is likely to be

A about 350 rpm

B about 250 rpm

C about 175 rpm

D about 125 rpm

ANS:D - about 125 rpm

Average output voltage ∝ cos a and therefore reduced to 0.707 of the value for a = 0. Speed is nearly proportional to voltage.