Electrical Machines
Semi closed slots or totally closed slots are used in induction motors, essentially to

 decrease starting torque
 increase pull out torque
 improve starting torque
 reduce magnetising current and improve power factor

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

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

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