Why can’t an induction motor run at synchronous speed?

The rotor is placed in such a way that this magnetic field induces a current in the rotor. … Due to this difference in flux, the rotor will experience a torque and will start to rotate at speed less than synchronous speed due to lagging. So, theoretically, the Induction motor can never run at synchronous speed.

Why Cannot an induction motor run at synchronous speed?

The induction motor can’t run at synchronous speed because it is not possible to run the motor without load. Even the motor is at no load, there would be core loss,copper loss and air friction loss.In a nut shell, the motor slip can not be zero in any case.

Can induction motor runs above synchronous speed?

If an external mechanical system drives the rotor above synchronous speed, the induction machine acts as a generator. If the rotor is rotating below synchronous speed, the induction machine is a motor.

Can an induction motor be synchronous?

An induction motor is a single excited machine. Its armature winding is energized from an AC source and its field winding from a DC source. Its stator winding is energized from an AC source. It always runs at synchronous speed.

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Why do motors run at synchronous speed?

A synchronous motor runs at synchronous speed only because it is meant to run like that . It cannot run on a speed other than synchronous speed. Stator(N) links with Rotor(S).

What is the need of starter for induction motor?

Such a device which limits high starting current is called a starter. Let us study in detail why starter is required for an induction motor. At starting time, the speed of the motor is zero and slip is at its maximum i.e. unity. So magnitude of the rotor induced emf is very large at start.

What happens if fifth harmonics is given to induction motor?

It will rotates in normal operation. Either short circuit or open circuit occurs. The sinusoidal components having frequency five times of fundamental are known as fifth harmonics. … Hence induction motor will rotates in reverse direction because of reverse phase sequence of fifth harmonics.

Which motor has highest no load speed?

Explanation: At no load, armature current tends to zero, flux φ tends to zero, where speed is inversely proportional to the flux, speed will tend to infinity. Thus, no load speed of DC series motor is highest.

What is the speed of synchronous motor?

The synchronous speed is the speed of the revolution of the magnetic field in the stator winding of the motor. It is the speed at which the electromotive force is produced by the alternating machine.



Synchronous Speed.

Number of Poles Synchronous Speed NS in r.p.m
10 600
12 500
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What will happen if induction motor speed reaches synchronous speed?

Due to this difference in flux, the rotor will experience a torque and will start to rotate at speed less than synchronous speed due to lagging. So, theoretically, the Induction motor can never run at synchronous speed. … This will result in no torque on the rotor, and it will stop moving due to this.

What would happen if synchronous speed is equal to rotor speed?

This in turn reduces rotor voltage, current and torque (it also reduces the frequency of the rotor current). If the rotor reached synchronous speed, there would be no movement of stator field relative to the rotor conductors, and no induced voltage, current or torque.

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