While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by

induction motor torque in field winding
induction motor torque in damper winding
eddy current and hysteresis torque in pole faces
reHetance motor torque due to saliency of the rotor E. all of the above methods

The correct answer is: E. all of the above methods.

When a salient pole synchronous motor is started by induction motor action, the stator winding is connected to an AC supply and the rotor is left open-circuited. The stator current creates a rotating magnetic field that induces a current in the rotor windings. This current creates its own magnetic field, which interacts with the stator field to produce a torque that starts the motor.

The torque produced by the induction motor action is proportional to the square of the stator current. The stator current is limited by the resistance of the stator windings and the applied voltage. As the motor accelerates, the stator current decreases and the torque produced by the induction motor action decreases.

To maintain a high starting torque, a field discharge resistance is connected across the field winding. This resistance increases the current in the field winding, which increases the magnetic field produced by the field winding. The increased magnetic field increases the torque produced by the induction motor action.

The eddy current and hysteresis torque in the pole faces are also present when the motor is started. These torques are due to the interaction of the stator field with the eddy currents and hysteresis losses in the pole faces. The eddy current and hysteresis torques are small compared to the torque produced by the induction motor action, but they can contribute to the starting torque.

The reluctance motor torque due to saliency of the rotor is also present when the motor is started. This torque is due to the difference in reluctance between the stator and rotor magnetic fields. The reluctance motor torque is small compared to the torque produced by the induction motor action, but it can contribute to the starting torque.

Therefore, the starting and accelerating torque is produced by all of the above methods.

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