Electrical Machines
In a star - delta starting of an IM

  applied voltage per stator phase is 57.7 % of a line volt
  reduced voltage is applied to the stator.
  resistance is inserted in the rotor.
  line voltage is 57.7 % of stator voltage.

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Electrical Machines
In dc machines, the field system has to be provided on stator unlike synchronous machines Where in it could be on any member, because

 commutator action is not possible otherwise
 it reduces field structure iron losses
 dc machines are comparatively low rating machines.
 it gives more uniform air-gap flux distribution

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Electrical Machines
Commutation in a DC machine may be explained as a process

 by virtue of which emf is induced in the armature conductors.
  in which magnetic field is set up.
 how alternate flux affects the main field flux.
  by which electric current in a coil is reversed.

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Electrical Machines
Which of the following is done in speed control of DC motor by field flux control?

 Inserting an additional resistance in the field circuit.
 Any of above.
 Inserting resistance to armature circuit and field circuit.
 Inserting an additional resistance in the armature circuit.

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