Electrical Machines
The compensating winding in a DC machine

  is located on pole shoes for avoiding the flashover at the commutator.
 is located in armature slots for compensation of the armature reaction.
  is located on pole shoes to avoid the sparking at the brushes.
 is located on commutating poles for improving commutation.

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Electrical Machines
The mmf produced by rotor currents of a 3 - Φ induction motor

  rotates at slip speed with respect to stator mmf.
  is at standstill with respect to stator mmf.
  rotates at the speed of rotor in the air gap.
  rotates at synchronous speed with respect to rotor.

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