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, 2, 5
 1, 3, 5
 1, 2, 6

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Electrical Machines
The synchronous reactance( Xs) is the

 reactance due to leakage flux
 reactance due to armature reaction of the machine
 combined reactance due to armature reaction and leakage flux
 reactance either due to armature reaction or leakage flux

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