In the A.C. series, motor compensating winding is employed to
Right Answer is:
Both 2 and 3
In the A.C. series, motor compensating winding is employed to reduce the effect of armature reaction & sparking in brushes.
Function of Compensating Winding
In the case of a single-phase ac series motor, two EMFs are induced in the armature conductors.
(a) Rotating emf
(b) Transformer emf
Due to this reason, the short-circuited coils across the brushes may experience both the above emf according to the position of the brushes. Thus, the outcome appears as excessive sparking at the brushes and poor power factor of the motor. So, the compensating winding to reduce this increased armature reaction is a must in the case of ac series motors. The two types of compensated ac series motors. These are as follows:
(a) Conductively compensated ac series motor
(b) Inductively compensated ac series motor
The performances of both the conductive and inductive compensations are similar. In the case of conductive compensation, the same current flows through the compensating winding and the armature winding.
But in the case of inductive compensation, the current developed in the compensating winding is totally by the method of induction. So, if properly designed and constructed, the same performance characteristics can be obtained both for conductively compensated and inductively compensated ac series motors.
To reduce sparking at the brushes on account of the transformer emf, high resistance leads to reduce circulating currents that can be connected between the armature coils and the commutator segments.
Hence to reduce the armature reaction and sparking at brushes the compensating winding is used.