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, 6
 1, 2, 5

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Electrical Machines
An ideal synchronous motor has no starting torque because

 rotor is made up of salient poles.
 rotor winding is highly reactive.
 relative velocity between the stator and rotor mmf’s is zero.
  relative velocity between stator and rotor mmf’s is not zero.

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