Electrical Machines
Under operating conditions the rotor conductor should be _________________ in induction motor.

  semi closed or semi opened.
  none.
  always opened.
  always closed.

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Electrical Machines
Consider the following statements : Interpoles in dc machines 1. reducearmature reaction effects in the interpolar region 2. have the same dimension as main polls 3. have their windings connected in series with the armature 4. have same number of turns as the armature 5. have the polarity same as that of the main pole ahead in a motor From these, the correct statements are

 1, 2 and 3
 1, 3 and 5
 1 and 3
 1, 2, 3 and 5

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Electrical Machines
Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

 2, 3 and 4
 1, 2, and 3
 1 and 3
 1, 2 and 4

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