Electrical Machines
Ward-Leonard system for controlling the speed of a DC motor is used where

 The speed in both the direction is required.
 The accuracy in speed control is required.
 All of above.
 Very fine speed control over the whole range from zero to normal speed is required.

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

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Electrical Machines
The compensating winding in a DC machine

 is located on commutating poles for improving commutation.
  is located on pole shoes to avoid the sparking at the brushes.
  is located on pole shoes for avoiding the flashover at the commutator.
 is located in armature slots for compensation of the armature reaction.

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Electrical Machines
In a 3 - Φ induction motor

  power factor at starting is high as compared to that while running.
  power factor at starting is low as compared to that while running.
  power factor at starting in the same as that while running.
  none of them.

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