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
In a DC generator, the armature reaction results in

 magnetization of leading and demagnetization of trailing pole tip.
  demagnetization of leading & magnetization of trailing pole tip.
 demagnetization of centers of poles.
  magnetization of inter poles.

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Electrical Machines
If two 8-pole dc machines of identical armature sare wound, one with lap winding and the other with wave winding, then

 wave-wound machine will have more rated voltage and less current
 wave-wound machine will have more rated current and more voltage
 lap-wound machine will have more rated voltage and more current
 lap-wound machine will have more rated voltage and less current

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