# Best answer: Why does an induction motor run at less than synchronous speed?

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Actual speed of the induction motor will be less than the synchronous 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.

## What happens when 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.

## Is it possible to run an induction machine as a motor at speed greater than synchronous speed?

The induction motor can’t be run above synchronous speed. Even with VFD, the actual speed of the motor is always less than the synchronous speed of the motor. In the case of slip ring induction motor, the motor can be run above its synchronous speed by feeding power to the rotor. No.

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## Why does the rotor run at a speed which is always less than the speed of the stator field?

3 Answers. In an induction motor, the speed of the rotor structure is always less than the speed of the stator field. However the rotor field rotates faster than the rotor structure so that the rotor and stator fields are synchronized with each other.

## What is the difference between the synchronous speed and the actual speed of an induction motor?

In a synchronous motor, the rotor and rotating magnetic field of stator rotate at the same speed and this speed is known as synchronous speed. In an induction motor, the rotor rotates at a speed less than the rotating magnetic field of the stator and the difference between these two speeds is called slip speed.

## 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.

## What is 120 in motor speed formula?

The equation for calculating synchronous speed is: S = 120 f/P speed = constant (120) times frequency of power source (60 Hz) divided by number of poles used in the motor (P).

## Can rotor speed be greater than synchronous speed?

An induction generator produces electrical power when its rotor is turned faster than the synchronous speed. … For example, a motor operating at 1450 RPM that has a synchronous speed of 1500 RPM is running at a slip of +3.3%. In normal motor operation, the stator flux rotation is faster than the rotor rotation.

## What is the speed of synchronous motor?

The synchronous speed of an AC motor is determined by the frequency of the source and the number of poles. The RPM is calculated by multiplying the frequency times 60 and dividing by the number of pairs of poles. This was explained in Chapter 6. Some motors are designed to operate at synchronous speed.

## Why is the efficiency of an induction motor so poor at high slips?

So (1—s)P2 is converted to mechanical power, to which you can subtract mechanical losses to get shaft output. From this it is clear that for a given input the shaft output decreases as slip increases and hence the efficiency decreases at higher slip in the stable operating region. 