Question

What will be the compensating winding provided in the case of a conductively compensated DC motor?
(A) as separate winding,
(B) In parallel with armature winding,
(C) in parallel with field winding,
(D) in series with the armature winding.

Answer 1

Hint
In a DC motor the compensation winding is provided in order to reduce the stator field distortion, the compensated winding is wound in order to reduce the sparking of the commutation.

Complete step by step solution
The compensation winding is a type of a winding implanted in the pole faces of an AC current or DC machine and are attached in sequence with the armature winding. Then the magnetic field of the winding neutralizes the cross-magnetizing field of the armature.
The compensation windings consist of a sequence of coils implanted in the slots of the pole faces. These coils are attached in series with the armature. The sequence attached compensating windings produce a magnetic field that varies straight with the armature current. Since the compensation windings are wound to create a field that defies the magnetic field of the armature, they tend to cancel the cross-magnetizing effect of the armature magnetic field. The neutral plane will stay stationary and the original place for all values of armature current. Due to this, once the brushes have been placed correctly, they don’t have to be displaced again.
Therefore, in case of a conductively compensated DC motor, the compensating winding is provided in series with the armature winding.
Hence, the option (D) in series with armature winding is the correct answer.

Note
Regardless of the armature wires which are next to the wires that are bearing the current in the opposing direction, the wires of the armature still encounter magnetic force from relation with the field flux. Due to the pole face, the armature’s magnetic moment force is counteracted by the compensating winding magnetic moment force.