During hunting of synchronous motor

When the motor runs at synchronous speed in the steady-state condition, maintain a constant value of the torque angle δ. If a sudden load change occurs torque angle δ gets disturbed. This disturbance changes the speed of the motor therefore in a synchronous motor hunting takes place when the load varies and the damper bar develops torque.

Causes of hunting:

• Periodic variation of load
• Sudden changes in load
• Faults occur in the system when supplied by the generator
• Sudden change in the field current
• Cyclic variations of the load torque

Effects of Hunting:

• It can lead to loss of synchronism
• It can cause variations of the supply voltage producing undesirable lamp flicker
• The possibility of resonance condition increases. If the frequency of the torque component becomes equal to that of the transient oscillations of the synchronous machine, resonance may take place
• Large mechanical stresses may develop in the rotor shaft
• The machine losses increases and the temperature of the machine rises

Reduction of Hunting:

• Use of damper windings
• Use of flywheels