Electrical Machines
The direction of rotation of a 3 - Φ induction motor is clockwise when it is supplied with 3 - Φ sinusoidal voltage having phase sequence A - B - C. For counterclockwise rotation of motor, the phase sequence of the supply should be

 B - C - A or C - A - B.
 C - A - B.
  A - C - B.
 B - C - A.

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Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

 field resistance was higher than critical resistance
 field winding was wrongly connected
 there was a break in the armature circuit
 field system lost residual magnetism

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Electrical Machines
The compensating winding in a DC machine

  is located on pole shoes to avoid the sparking at the brushes.
 is located in armature slots for compensation of the armature reaction.
  is located on pole shoes for avoiding the flashover at the commutator.
 is located on commutating poles for improving commutation.

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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, 4, 6
 1, 2, 5
 1, 3, 5

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