Electrical Machines
When an electric train is moving down a hill, the DC motor will operate as

 DC shunt motor.
 DC shunt generator.
  DC series motor.
  DC series generator.

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

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

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