Electrical Machines
Armature reaction in a DC machine

  makes an angle of 90° with the main pole axis.
 is in direct opposition to the main poles.
 is in the same direction as the main poles.
 makes an angle with the main pole axis which is load dependent.

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

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

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