Hunting is a phenomenon that occurs in synchronous motors when there is a sudden change in load. The rotor of the motor will begin to oscillate around its synchronous speed. This oscillation can cause the motor to lose synchronism and stall.
Here are some of the reasons why hunting occurs in synchronous motors:
When the load on a synchronous motor changes, the torque angle changes. This causes the rotor to speed up or slow down, depending on whether the load is increased or decreased.
The rotor of a synchronous motor is not perfectly rigid. This means that it can bend slightly when the torque angle changes. This bending causes the rotor to oscillate around its synchronous speed.
Hunting can be prevented by:
Using a soft starter or a variable frequency drive (VFD) to gradually increase the speed of the motor when the load is increased.
Increasing the field excitation of the motor. This will make the motor more resistant to changes in load.
Using damper windings. Damper windings are short-circuited windings that are placed on the rotor of the motor. They help to dissipate the energy of any oscillations that do occur.
If hunting does occur, it can be stopped by:
Reducing the load on the motor.
Increasing the field excitation of the motor.
Applying a braking torque to the motor.
Hunting can damage the motor if it is not prevented or stopped. The motor can overheat, the bearings can wear out, and the windings can be damaged.