Power Electronics - Engineering

Q1:

A dc separately excited motor has a constant field current. The armature is fed from a single phase supply through a semi-converter. When a = 0, speed is 600 rpm. If a = 90°, the speed is likely to be

A about 300 rpm

B about 150 rpm

C about 75 rpm

D about zero

ANS:A - about 300 rpm

Average output voltage is reduced to 50% if a = 90°. Hence speed is also reduced to 50%.