Electrical Machines
Crawling in an induction motor is due to

  time harmonics in supply.
  slip ring rotor.
  insufficient starting torque.
  space harmonics produced by winding currents.

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Electrical Machines
If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

 changes to 0.5 times the original value
 changes to three times the original value
 changes to 1.5 times the original value
 remain the same as the original

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Electrical Machines
In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation. Now, if the brushes are given a lead of 90° (electrical), then the MNA will

 coincide with the GNA
 shift forward by more than 90°
 shift forward by 90°
 shift forward by less than 90°

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