Electrical Machines
The 3 - Φ induction motors are, by a very considerable margin, the most widely used AC motors as

  they are capable of operation under range of leading and lagging pf.
  they have maximum efficiency and maximum starting torque.
  they have very good speed regulation.
  these are cheaper in cost, simple and rugged in construction.

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Electrical Machines
Cogging of induction motor occurs at

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

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