How Does A Synchronous Motor Rotate?

A synchronous motor is one in which the rotor normally rotates at the same speed as the revolving field in the machine. The stator is similar to that of an induction machine consisting of a cylindrical iron frame with windings, usually three-phase, located in slots around the inner periphery.



Which of following speed is known as synchronous speed?

Explanation : The speed at which stator magnetic field rotates is N s which is also called synchronous speed.


What two factors determine synchronous speed?

The speed of the rotating stator field is called the synchronous speed. The frequency of the power supply and the number of poles of the machine determine the synchronous speed.


Does motor runs at synchronous speed only?

The synchronous motor is made to rotate at synchronous speed only. The reason behind this is Magnetic Locking between stator and Rotor.


Can a rotor rotate at synchronous speed?

No, An Induction motor cannot rotate at syn speed as at that speed the rotor cannot cut the rotating field resulting in no induced emf in the rotor and hence no current and no torque. So it will slip back and speed will be reduced to such a value to produce the torque and hence power to at least overcome losses.


Why does an induction motor never run on synchronous speed?

The Induction Motor cannot run at Synchronous speed because the Slip is never zero in an Induction Motor.


Why a synchronous motor Cannot run any speed other than the synchronous speed?

An induction motor always runs at a speed less than synchronous speed because the rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate, but due to the lagging of flux current in the rotor with flux current in the stator, the rotor will never reach .


What is the relation between rotor speed and synchronous speed?

The friction and windage would immediately cause the rotor to slow down. Hence, the rotor speed (Nr) is always less than the synchronous speed (Ns). This difference in speed is known as slip speed and it depends upon the mechanical load on the motor.


What is meant by synchronous speed?

Definition of synchronous speed

: a definite speed for an alternating-current machine that is dependent on the frequency of the supply circuit because the rotating member passes one pair of poles for each alternation of the alternating current.


What is synchronous speed of motor?

Synchronous speed is the speed of rotation of the magnetic field in a rotary machine. An induction motor always runs at a speed less than synchronous speed. The rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor rotate.


How can we change the speed of motor?

AC motors are constant speed devices but their speed can vary if you change the input voltage or frequency or the windings that make the motor rotate. The most common and efficient way of changing the speed is to vary the frequency by using an inverter as the power supply.


Which motor can be rotate by synchronous speed?

1.2 Synchronous Motors

Synchronous motors, as the name implies, rotate at a constant (synchronous) speed. The rotor of this type of motor is a wound rotor, which receives the excitation (magnetizing) current from its excitation system (a separate direct current source with controller).


Why is synchronous speed greater than rotor speed?

The reason for this is if the armature turns exactly at synchronous speed, then the magnetic field of the stator windings no longer cuts the rotor windings. Under this condition, no current would be induced to the rotor windings.


Is speed control possible in synchronous motor?

Speed of synchronous motors can be controlled using two methods called open loop and close loop control. Open loop contol is the simplest scalar control method where motor speed is controlled by independent frequency control of the converter.


How does a synchronous motor rotate?

A synchronous motor is one in which the rotor normally rotates at the same speed as the revolving field in the machine. The stator is similar to that of an induction machine consisting of a cylindrical iron frame with windings, usually three-phase, located in slots around the inner periphery.


Why rotor speed is less than synchronous speed?

The actual rotor speed is always less than synchronous speed so as to produce current in the rotor bars. Two terms are used to define relative motion between rotor and rmf. One of them is slip speed. Slip speed is defined as the difference between synchronous speed and rotor speed.


Why does synchronous motor runs at synchronous speed?

Why a 3-phase synchronous motor will always run at synchronous speed? Because of the magnetic coupling between the stator poles and rotor poles the motor runs exactly at synchronous speed.


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22-Jul-2022

Education

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