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## Saturday, March 11, 2023

Synchronous motors are a type of AC motor that operate at a constant speed that is synchronized with the frequency of the power supply. They are commonly used in applications where precise speed control is required, such as in industrial equipment and large machinery. One of the important aspects of synchronous motor operation is hunting, which refers to the small oscillations in speed that can occur when the load on the motor changes. In this blog post, we will explore ' what is hunting in synchronous motor and why it occurs '.

# what is hunting in synchronous motor ?

When a load is applied to a synchronous motor, the amount of torque required to maintain the speed of the motor increases. If the load on the motor increases beyond a certain point, the motor may begin to slow down. When this happens, the magnetic field of the rotor can become misaligned with the magnetic field of the stator. This misalignment creates a torque that opposes the direction of rotation of the motor, which causes the motor to speed up again. This process of the motor speeding up and slowing down in response to changes in load is known as hunting.

At steady state operation, electromagnetic torque is equal and opposite to load torque, known as equilibrium condition. Also, rotor runs at synchronous speed by maintaining constant torque angle ( Î´ ). On sudden changing in load torque, this equilibrium is disturbed and speed is changed.

Ï„eÏ„load = J dÏ‰M / dt

Where, Ï„e = torque at equilibrium

J = moment of inertia

Ï‰= angular velocity of rotor

Also,

Ï„e = 3 VEf sind Î´ / Ï‰s X

If sudden increase in load, load torque also increase and motor will slowly rotating. Motor will try to regain its equilibrium condition and synchronous speed, for that torque angle ( Î´ ) is increased which is given above. If Î´ increase, torque also increase and motor is accelerates & gain synchronous speed. But the value of Î´ is larger than required value Î´1 so rotor speed will go beyond the synchronous speed which will decrease Î´. At a point both  motor torque and load torque will become equal but the problem is equilibrium is not restored because of large value of rotor speed than synchronous speed. Hence, rotor will swing backward and Î´ decrease which value will less than required Î´1 and slow down the speed. Again this process will repeat again and again so we can say that rotor will swings around synchronous speed. This process is also similar while decreasing load.

what is hunting in synchronous motor ?  The phenomenon of oscillation of the rotor about its equilibrium position is called hunting.

### Hunting Reason of synchronous motor

Hunting may occur for a number of reasons. Some of them are:-
1. Sudden change in load on motor shaft.
2. Sudden change in motor field current.
3. Fault occur in the system.
4. One common cause of hunting is an imbalance in the load on the motor. If one part of the load is heavier than another, the motor may experience uneven torque, which can cause hunting.
5. Another cause of hunting is variations in the power supply frequency. If the frequency of the power supply fluctuates, the speed of the motor will also fluctuate, which can cause hunting.
6. In addition, hunting can occur if the motor is not properly tuned to the load it is driving. If the motor is over-tuned, it may be too sensitive to changes in load, which can cause hunting.

### Effect of hunting

The effects of hunting on synchronous motor performance can vary depending on the severity of the oscillations. In some cases, hunting may not have a significant impact on the operation of the motor. However, in other cases, hunting can cause damage to the motor and the equipment it is driving. For example, if hunting causes the motor to speed up and slow down rapidly, it can create excessive vibration that can damage bearings and other components. Hunting can also cause the motor to draw more current than normal, which can lead to overheating and damage to the windings. Some effect are as follows:-
1. It may cause loss of synchronism.
2. The machine loss increase and lead temperature increase.
3. Resonance may occur
4. Large mechanical stress on rotor shaft
5. It may cause varying supply voltage

### Prevention of synchronous motor

To prevent hunting in synchronous motors, it is important to properly tune the motor to the load it is driving. This involves adjusting the settings of the motor control system to ensure that the motor is not over-tuned or under-tuned. It is also important to ensure that the load on the motor is balanced and evenly distributed. If the load on the motor is unbalanced, it can create uneven torque, which can cause hunting. In addition, it is important to ensure that the power supply frequency is stable and consistent. If the frequency of the power supply fluctuates, it can cause hunting. Some reduction technique are:-
1. Use damper winding
2. Use flywheel which increase the inertia of prime mover for constant speed in load variation.
3. Design suitable synchronous motor with suitable synchronizing power coefficient.

In conclusion, hunting is a phenomenon that occurs in synchronous motors when the motor oscillates in speed in response to changes in load. Hunting can be caused by a number of factors, including load imbalances, variations in power supply frequency, and improper tuning of the motor. The effects of hunting on motor performance can vary, but in some cases, it can cause damage to the motor and the equipment. I think you understand ' what is hunting in synchronous motor '