Electrical Machines
In DC machines, the interpoles are provided

  both (B) and (C).
  to make commutation spark less.
 to counteract the reactance voltage and the cross-magnetizi
 to counteract demagnetizing effect of armature mmf in commutating zone.

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Electrical Machines
Consider the following statements regarding the speed control of dc motors : 1. ward-leonard method is suitable forconstant-torque drives 2. Ward-leonard method is suitable for constant-power drives 3. field-control method facilitates speed control below base speed 4. Armature-resistance control method is more efficient than ward-leanard method 5. Field-control method is suitable for constant-torque drives 6. Armature-resistance control method is suitable for constant-torque drives From these, the correct answer is

 1, 3, 5
 1, 4, 6
 1, 2, 6
 1, 2, 5

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Electrical Machines
For a single phase capacitor start induction motor which of the following is valid?

 None of these.
  Rotation can be changed by reversing main winding terminals.
 Rotation can be changed by interchanging supply terminals.
 Direction of rotation cannot be changed.

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