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

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

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

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

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