Electrical Machines
A 4 pole lap wound dc generator has 4 brushes, if one of the brush is damaged, what will be the change in V, I and P ratings

 V/2, I/2 and P/4
 V, I and P
 V/2, I and P/2
 V, I/2 and P/2

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Electrical Machines
Interpoles in a DC motor must be

 Series excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.

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Electrical Machines
In DC machines, the interpoles are provided

  to make commutation spark less.
 to counteract the reactance voltage and the cross-magnetizi
  both (B) and (C).
 to counteract demagnetizing effect of armature mmf in commutating zone.

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Electrical Machines
Cogging in induction motor occurs when

 number of stator teeth - number of rotor teeth = even number.
 number of stator teeth - number of rotor teeth = 0.
 number of stator teeth - number of rotor teeth = negative number.
 number of stator teeth - number of rotor teeth = odd number.

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