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

Varying the line voltage

Varying the field excitation

Increasing the speed of motor

Decreasing the speed of motor