Electrical Machines
A 240 V DC series motor takes 40 A when giving its rated output at 1500 rpm. Its resistance is 0.3 ohms. The value of resistance which must be added to obtain rated torque at 1000 rpm is

 1.9 ohms.
 6 ohms.
 2.2 ohms.
 5.7 ohms.

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

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

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

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