Electrical Machines
A separately-excited dc motor has an armature resistance of 0.5 Ω. It runs off a 250 V dc supply Drawing an armature current of 20 A at 1500 rpm. The torque developed for an armature current Of 10 A, for the same field current, will be

 15.6 Nm
 15.92 Nm
 16.55 Nm
 15.28 Nm

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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

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

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Electrical Machines
In case of 3 - Φ IM, plugging means

  pulling the motor directly on line without a rotor.
  starting the motor on load which is more than the rated load.
  locking of rotor due to harmonics.
  interchanging two supply phases for quick stopping.

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