Electrical Machines
In a DC machine, which of these parameters remain the same whether it runs as a DC motor or a DC generator?

 Mechanical power.
 Armature current.
 Induced emf.
 Can not be determined.

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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, 4, 6
 1, 2, 6
 1, 2, 5
 1, 3, 5

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Electrical Machines
What is/are the necessary conditions for voltage build up in self excited generator?

 Poles should contain residual flux.
All of these
 Field winding should be properly connected to armature winding.
 Field winding resistance should be less than critical resistance.

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