Electrical Machines
For a given torque, reducing divertor resistance of a DC series motor

  Decrease in speed but armature current remains the same.
  Increase in speed but armature currnet remains the same.
  Increase in speed demanding more armature current.
  Decrease in speed demanding less armature current.

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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 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.
  they have very good speed regulation.

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