Electrical Machines
A DC series motor drawing an armature current of Ia is operating under saturated magnetic conditions. The torque developed in the motor is proportional to

 Ia
 I/Ia2
 1/Ia
 Ia2

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

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

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Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

 field resistance was higher than critical resistance
 field winding was wrongly connected
 field system lost residual magnetism
 there was a break in the armature circuit

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