Electrical Machines
In dc machines, the armature windings are placed on the rotor because of the necessity for

 commutation
 development of torque
 electromechanical energy conversion
 generation of voltage

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Electrical Machines
Which of the following represents the commutator pitch?

 The distance between the staring of first coil and its next successive coil
 Number of conductors spanned by one coil at the front end of the armature.
 Number of commutator segments between two successive coils.
 Number of conductors spanned by one coil at the back end of the armature.

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Electrical Machines
Consider the following statements: To control the speed of a dc shunt motor above the base speed over a reasonably wide range, the motor must 1. have compensating winding 2. have interpole winding 3. be started using a 3-point starter 4. be started using a 4-point starter Of these statements

 1, 2 and 4 are correct
 1, 2 and 3 are correct
 2 and 4 are correct
 1 and 3 are correct

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Electrical Machines
In a 3 - Φ induction motor

  power factor at starting in the same as that while running.
  none of them.
  power factor at starting is high as compared to that while running.
  power factor at starting is low as compared to that while running.

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