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

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

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Electrical Machines
Two 3-phase AC generators are such that one has twice the linear dimensions of the other. The field windings of each are excited to give identical sinusoidal air-gap flux density waveform. Both have the same number of stator slots and identical winding patterns. The conductor/slot in a big generator is K times that of the smaller one. The value of K to get equal no load voltage at same frequency is

 1/4.
 8.
 4.
  1/2.

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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, 3, 5
 1, 2, 5
 1, 2, 6
 1, 4, 6

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