Electrical Machines
The introduction of interpoles in between the main poles improves the performance of a dc machine, because

 the flux waveform is improved with reduction in harmonics
 the inequality of air-gap flux on the top and bottom halves of the armature is removed
 a counter-emf is induced in the coil undergoing commutation
 the interpoles produce additional flux to augment the developed torque

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
The damper windings also called the squirrel cage windings or damper grids

  consists of short-circuited copper bars embedded in the field pole faces.
  both (A) and (B).
  are provided on the stator for improving power factor.
  are provided in a synchronous motor to make it self starting.

ANSWER DOWNLOAD EXAMIANS APP