What is synchronous motor? What is the method of starting synchronous motor? Write the characteristics of synchronous motor?

 

What is synchronous motor? What is the method of starting synchronous motor? Write the characteristics of synchronous motor?

 

 

What is synchronous motor? What is the method of starting synchronous motor? Synchronous Motor: Synchronous motor is a motor that rotates at a fixed speed from No Load to Full Load, i.e. it rotates all 120. time at synchronous speed (Ns p ). The speed of rotation of this motor does not change with load change like other motors, but its speed changes with change in number of poles or supply frequency. Its speed is inversely proportional to the number of poles, and proportional to the frequency.

 

Synchronous motor starting method: 1. With the help of DC Motor. 2. With the help of Pony Motor. 3. With self-starting synchronous motor. 4. With the help of synchronous induction motor. 5. With the help of Exciter.

 

 

Write the characteristics of synchronous motor? 1. It always rotates at the same speed in No Load and Full Load conditions. 2. There is no slip in it. 3. Can be run as an alternator. 4. It cannot turn on by itself. 5. Its stator and rotor have the same number of poles. And its structure is the same, it is called Alternator 6. It can be run on any P. f.

What is meant by hunting or phase swinging of synchronous motor? Write its reasons, difficulties and remedies? Answer: Hunting or Phase Swinging: When a synchronous motor is operated on a continuously varying load or the pulsating of the supply line varies, the speed of the motor fluctuates continuously with it.

 

This state of the motor is called hunting or banana-oscillation or phase swinging. Causes of Hunting: Hunting can occur in a synchronous motor due to the following reasons. 1. When the shaft of a synchronous motor simultaneously decreases, increases or removes the load or applies a continuously varying load. If the supply frequency is variable. 2. 4. If the synchronous motor is connected to a very long transmission line.

GUIDE OPTIMU Disadvantages : Hunting in synchronous motor has the following disadvantages. 1. The current and power consumption of the motor varies greatly. 2. The motor puts a lot of stress on the mechanical parts and damages them. For example, bearings, shafts and pulleys can corrode, rub or break. 3. Motor windings may burn. 4. Over hunting may cause the motor to stop.

 

Remedies for hunting: In synchronous motor, hunting is eliminated mainly by using damper winding or amortisseur (Amortisseur) Moreover, all the other methods used are: 1. Well using the “Dashpot” with the governor. 2. Uses heavy flywheels. 3. A thick copper sheet is used around the field pole.

The practical areas of synchronous motor are given below: 1. These motors are used as synchronous capacitors or synchronous condensers to improve power factor in transmission lines and mills. 2. Synchronous reactors are used to make up the shortfall in the transmission line under different load conditions and to keep the voltage equal. 3. Synchronous motors are used where constant speed must be maintained under all load conditions. 4. Synchronous motors are useful in all applications where the motor needs to be rotated in both directions.

 

The methods are given below: 1. D. Starting with C motor. 2. Synchronous motor with self-starting capability. 3. Starting as a synchronous induction motor. 4. Starting with “pony” motor. 5. Starting with exciter.

 

Starting Process of Synchronous Motor: At present, damper winding is used in almost all modern synchronous motors. The following process is employed while starting a synchronous motor with damper winding. 1. First the main field winding is short circuited. 2. Then the auto transformer starter has to supply low voltage to the stator terminals so that the motor can run.3. When the motor starts rotating at its normal speed, the short-circuit field winding is released from the short-circuit condition by a low value d. C excitation is given. If the excitation is sufficient, the machine will enter the synchronism state. 4. Then full supply voltage is applied to the stator. Auto starter is not required in this condition. 5. At this stage, the synchronous motor is arbitrarily d. C can be manipulated to any power factor by changing the excitation.