Compensated Induction Motor (No-Lag Type Motor):
This is an improvement of the plain induction motor designed to operate at approximately unity or slightly leading power factor over the whole range of loads. The usual type of compensated induction motor is no-lag type motor, which consists of a primary winding placed on the rotor and the secondary winding on the stator, as shown in Fig. 1.35.
The rotor consists of an additional winding, known as commutator winding, whose emfs are collected by the brushes from the commutator and injected into the secondary winding in such a way that power factor improvement is accomplished.
No-lag motor was developed earlier and Schrage motor is actually modification form of the no-lag motor. In this motor phase of the emf can be varied but not the magnitude.