Electrical Machines
Under which of the following conditions hunting of synchronous motor is likely to occur ?

  Small and constant load.
  Over-excitation.
  Periodic variation of load.
  Over-loading for long period.

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

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Electrical Machines
An inverted V curve of synchronous motor shows variation of

 supply voltage and field current at constant excitation.
 supply voltage and excitation current at constant load.
 power factor and supply voltage during hunting.
  power factor and DC excitation at constant load.

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