Electrical Machines
Which of the following methods are used to control the speed of DC motors is

All of these
 field current control
 supply voltage control
 armature circuit resistance control

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Electrical Machines
In a synchronous motor when the rotor speed exceeds the synchronous speed during hunting

  negative sequence currents are generated.
  the damper bars develop induction generator torque.
  the damper bars develop synchronous motor torque.
  the damper bars develop induction motor torque.

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Electrical Machines
The synchronous reactance( Xs) is the

 combined reactance due to armature reaction and leakage flux
 reactance due to leakage flux
 reactance due to armature reaction of the machine
 reactance either due to armature reaction or leakage flux

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