Electrical Machines
In a 3 - Φ IM in order to eliminate cogging the number of stator slots must be

  an integral multiple of number of rotor slots.
  either (B) or (C).
  equal to number of rotor slots.
  unequal to number of rotor slots and skewed in shape.

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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, 2, 6
 1, 3, 5
 1, 2, 5
 1, 4, 6

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

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

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