Electrical Machines
Cogging of induction motor occurs at

 high voltage and when stator and rotor poles are equal.
 low voltage and when stator and rotor poles are equal.
 high voltage and when stator and rotor poles are not equal.
 low voltage and when stator and rotor poles are not equal.

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Electrical Machines
In case of 3 - Φ IM, plugging means

  starting the motor on load which is more than the rated load.
  locking of rotor due to harmonics.
  pulling the motor directly on line without a rotor.
  interchanging two supply phases for quick stopping.

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