# Synchronous Machines: Why Can't Induction Machines Run at Synchronous Speed?

• smruti
In summary, Synchronous machines can only run at a certain speed, whereas induction machines can run at any speed. The difference in speeds is called the slip, and it produces a current that magnetizes the rotor and creates a torque. Higher slip results in a higher force.
smruti
synchronous machine can run at synchronous speed but why can't induction machine run at synchronous speed?

smruti said:
why can't induction machine run at synchronous speed?

Asynchronous motors contain a rotor with a squirrel cage. When the cage has a different rotational speed than the speed of magnet field from the stator, an emf will be induced in cage, which results in a current. This current magnetizes the rotor, and a torque arises.

The difference in speeds is called the slip, which by synchronous speed = 0. No slip → no emf → no current → no magnetic field in rotor → no torque.

Synchronous motors can only run at synchronous speed.

The force exercised on a wire through which a current flows in a magnetic field it is F=K*I*B- B=magnetic flux density [induction].Based on Newton second law the action [force]=reaction[force] that means this force acts on both-stator and rotor and rotor rotates.
In a synchronous machine we have a magnetic field in the rotor.
In asynchronous machine we haven’t. In order to create a magnetic field we need current. If the rotor run with the same velocity as the magnetic field produced by stator –as Hesch explained it very well-no current will appear in the rotor winding-squirrel cage or wounded rotor or else- that means no force will act on the rotor.
The speed difference-the slip=[synchronous speed-rotor speed]/synchronous speed-will produce a current at a low frequency =slip*supply frequency. Higher slip higher force.
As the load is increasing the required force increases and then the slip increases.

Higher slip higher force.
As the load is increasing the required force increases and then the slip increases.

Well, yes, with some limitations. Typical torque characteristic for an asynchronous motor:

Thank you, Hesch.I agree with you of course.

## 1. Why can't induction machines run at synchronous speed?

Induction machines use electromagnetic induction to create motion. This means that the rotor, or the rotating part of the machine, must always run at a speed slightly slower than the speed of the rotating magnetic field in the stator, or stationary part of the machine. This difference in speed is known as slip and is necessary for the induction process to occur.

## 2. Can induction machines be modified to run at synchronous speed?

No, induction machines cannot be modified to run at synchronous speed. The design and operation of these machines rely on the principle of slip, so changing the speed would significantly alter their functioning. Additionally, making significant changes to the design of the machine would be expensive and impractical.

## 3. What are the advantages of synchronous speed in machines?

Synchronous speed allows for better control and efficiency in machines. It allows the machine to run at a consistent speed, making it easier to synchronize with other machines and maintain a stable power output. Additionally, synchronous speed allows for better energy conversion and reduces losses due to slip.

## 4. Are there any machines that can run at synchronous speed?

Yes, synchronous machines, as the name suggests, are designed to run at synchronous speed. These include synchronous generators, motors, and alternators, among others. These machines use a different principle of operation, known as synchronous induction, which allows them to run at a constant speed.

## 5. Can synchronous machines be used in all applications?

No, synchronous machines are not suitable for all applications. They are typically used in high-power and precision applications where constant speed and precise control are necessary. Induction machines, on the other hand, are more versatile and can be used in a wider range of applications, including low-power applications.

Replies
37
Views
4K
Replies
1
Views
2K
Replies
14
Views
3K
Replies
12
Views
2K
Replies
4
Views
3K
Replies
9
Views
1K
Replies
14
Views
4K
Replies
3
Views
1K
Replies
5
Views
2K
Replies
5
Views
1K