Produce high voltage to initiate the rotation

Produce high current to start rotate the motor

Produces torque and runs near in synchronous speed

Produce a high magnetic-field to maintain a constant speed

Insufficient excitation

Defective pony motor

Open in damper winding

Short in damper

Varying the motor load

Varying the rotor excitation

Varying stator voltage in motor

Varying stator current in motor

Maintain power factor

Excite the field winding

Maintain constant speed

Start the synchronous motor

SCR converter

Rotary converter

Motor generator set

Mercury arc rectifier