Electrical Machines
To have sparkless commutation, the armature reaction effect in a DC machine is neutralized by

 shifting the brush axis from GNA to MNA.
 fixing the brush axis inline with the pole axis.
 increasing field excitation.
  compensating winding and commutating poles.

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

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

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Electrical Machines
In a synchronous generator with constant steam input supplies power to an infinite bus at a lagging power factor. If the excitation is increased

 power angle increase and power factor decrease
 both power angle and power factor increase
 both power angle and power factor decrease
 power angle decrease and power factor increase

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