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

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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 …

## Can the rotor of an induction motor reach the synchronous speed?

Note – an induction motor will never reach its synchronous speed. If it did – the rotor would appear to be stationary to the rotating stator field since it would rotate with the same speed. With no relative motion between stator and rotor field no voltage will be induced in the motor.

## What happens to the rotor of a 3 phase induction motor if its speed attains to synchronous speed?

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. In order that the no-load losses can be met, the rotor attains a speed less than synchronous.

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induction motor

## What is the synchronous speed of an induction 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.

## What happen when induction motor run at synchronous speed?

An induction motor can’t development torque at synchronous speed because an induction motor can’t run at synchronous speed because if it runs at synchronous speed the relative speed between the rotor and stator R.M.F will be zero so the torque will be zero.

## Which type of motor are used in most?

Ok, let’s take a short overview of twelve most basic motor types used for different industrial electric drives:

• DC Series Motor.
• DC Shunt Motor.
• Cumulative Compound Motor.
• Three phase Synchronous Motor.
• Squirrel Cage Induction Motor.
• Double Squirrel Cage Motor.
• Slip ring Induction Motor.
• Single phase Synchronous Motor.

## How does an induction motor start?

When the supply is connected to the stator of a three-phase induction motor, a rotating magnetic field is produced, and the rotor starts rotating and the induction motor starts. … At the time of starting, the motor slip is unity, and the starting current is very large.

## What is cogging in 3 phase induction?

The phenomenon of Magnetic Locking between the stator and the rotor teeth is called Cogging or Teeth Locking. Even after applying full voltage to the stator winding, the rotor of a 3 phase induction motor fails to start. Thus, a locking is created between the stator and rotor teeth. …

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## Why are motors not self starting?

Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. … Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.

## Why do induction motors have air gaps?

The air gap refers to an actual physical gap in an electric motor that separates the moving rotor and the stator core. This gap is a necessary part of motor design and the size of the air gap is one of the keys to motor performance and reliability.19 мая 2020 г.

## What is normal slip of an induction motor?

Because of this speed difference, the motor rotates at a speed slightly slower than the synchronous speed. Slip is normally expressed in percentage. Slip of a power induction motor is 2 to 3% when the motor is operated under the rated load.

## Why synchronous motor is a constant speed motor?

In the synchronous motor, rotor too have a DC excitation, so it produces a constant flux forming the electromagnetic poles on rotor which initially are stationary. … Even on loading, the speed is always constant but the torque angle (between stator and rotor magnetic poles) may vary.

## 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). Where does the 120 come from and what units does it have? There is RPM on one side and Cycles/second divided by #of poles on the other.

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## Can a VFD increase motor speed?

For applications that need a higher speed than what their motor currently offers, but that can’t afford to reduce the torque or power of the motor, a VFD is an optimal solution. As long as the motors are capable of handling the higher speed—Groschopp motors are—a control can be used to make the necessary adjustments.

## How do I calculate RPM?

How to Calculate Motor RPM. To calculate RPM for an AC induction motor, you multiply the frequency in Hertz (Hz) by 60 — for the number of seconds in a minute — by two for the negative and positive pulses in a cycle. You then divide by the number of poles the motor has: (Hz x 60 x 2) / number of poles = no-load RPM. 