Electrical Machines
The rotor slots are slightly skewed in squirrel cage induction motor to

 reduce the magnetic hum and locking tendency of rotor.
 increase the strength of rotor bars.
 provide ease of fabrication.
 decrease the amount of copper to be used.

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

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

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