Electrical Machines
Dummy coils are used for

 reducing armature reaction.
 mechanical balancing.
All of these
 increasing efficiency.

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Electrical Machines
The synchronous motor can be started by

  coupling it with a DC compound motor.
  providing damper winding in its rotor circuit.
  coupling it with a small AC induction motor called the pony motor.
  any of the above methods.

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