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, 4, 6
 1, 3, 5
 1, 2, 5
 1, 2, 6

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Electrical Machines
Cogging in induction motor occurs when

 number of stator teeth - number of rotor teeth = 0.
 number of stator teeth - number of rotor teeth = odd number.
 number of stator teeth - number of rotor teeth = negative number.
 number of stator teeth - number of rotor teeth = even number.

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Electrical Machines
What will happen if the the supply terminals are reversed in case of a DC shunt motor?

 The motor will run at its normal speed in the same direction as before.
 The motor will run much faster in the same direction.
 The motor will run in reverse direction.
 The motor will stop.

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