The compensating winding in a DC machine
Right Answer is:
Is located on pole shoes
Compensating windings are used to overcome the commutation and cross-magnetization effect of armature reaction, which causes high flux density in the trailing pole tip. Also, the coil under this tip can develop an induced voltage that is high enough to cause a flashover between nearby commutator segments.
The compensating winding in a DC machine is located on pole shoes.
Compensating winding is connected in series with the armature winding in such a way that the current flowing in them is directly opposite to the current flowing in the armature located just below the pole faces. Half of the conductors (say the left-hand side of the pole) is connected in series with the other half of the conductors (on the right side of the adjacent pole).
Physically, this coil is much closer to the commutation zone in which the air temperature can be high due to the commutation process. Therefore, the compensating windings are located on pole shoes to avoid flashover.