Working Principle of 3 phase squirrel cage Induction Motor

3 phase squirrel cage Induction Motor is one of the most popular types of AC electric motor which achieve the electromechanical energy conversion through stator and squirrel cage rotor by electromagnetic induction. That’s why it’s called squirrel cage induction motor.
Normally, we use the motors in industrial drives because they are rugged, reliable and economical.
By the way , the induction motor is also called as asynchronous motor because it runs at a speed lower than its synchronous speed.
In this article, I am going to focus on the working principle of the induction motor.
However, even before I do that, it is important to know the various parts of induction motor.

History
Nikola Tesla (July 10, 1856 – January 7, 1943), Serbian-American inventor, mechanical engineer, electrical engineer. He is considered to be one of the important promoters of commercialization of electricity because of the design of modern AC systems. On the basis of the theory of electromagnetic field discovered by Michael Faraday, Tesla invented the induction motor in 1887, and his theory of electromagnetism was the cornerstone of modern wireless communication and radio.

How a 3 phase squirrel cage Induction Motor Works?
Actually, when we give the stator winding AC power supply, the current flow in the coil will produce a magnetic flux in the coil.

Now, set the rotor windings to short circuit. The flux from the stator will cut the coils in the rotor, and the Faraday’s law of electromagnetic induction will cause the current to flow in the coil of the rotor due to the short circuit of the rotor coil.

The stator and rotor current flow produces two fluxes, one is the stator flux and the other is the rotor flux, and the rotor flux will lag behind the stator flux. Thus, the rotor will feel the torque that rotates the rotor in the direction of the rotating magnetic flux. Therefore, the speed of the rotor will depend on the AC power, and the speed can be controlled by changing the input power.

Inherent slip – unequal rotation frequency of stator field and the rotor

A three-phase power supply provides a rotating magnetic field in an induction motor

Parts of 3 phase squirrel cage Induction Motor
The rotor consists of a rotor core, a rotor winding and a rotating shaft. The rotor core is also part of the main magnetic circuit, generally by the thickness of 0.5mm silicon steel stack, the core fixed in the shaft or rotor bracket. The entire rotor is cylindrical. Rotor windings are divided into cage type and winding type.
Under normal circumstances, the induction motor rotor speed is always slightly lower or slightly higher than the rotating magnetic field speed (synchronous speed), so induction motor, also known as “induction motor.”
When the load of the induction motor changes, the rotor speed and slip rate will change, so that the rotor conductor in the electromotive force, current and electromagnetic torque corresponding changes to meet the needs of the load. In accordance with the positive and negative and the size of the slip, induction motor with motor, generator and electromagnetic brake three operating conditions.
What is a squirrel cage rotor?
A squirrel-cage rotor is the rotating part of the common “squirrel cage” induction motor. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. In operation, the non-rotating “stator” winding is connected to an alternating current power source; the alternating current in the stator produces a rotating magnetic field. The rotor winding has current induced in it by the stator field, and produces its own magnetic field. The interaction of the two sources of magnetic field produce torque on the rotor.

A Exploded view for parts of 3 phase induction AC motor

Characteristics of induction motors
1, start the torque is small, but its structure is simple, high reliability, high efficiency.
2, can be continuous operation.
3, the rated speed of the motor with the size of the load changes.
4, used in the case of no need to brake speed.
5, there are two-phase induction motor and three-phase induction motor.
6, three-phase induction motor power U (200V 50 / 60Hz), T (220V 50 / 60Hz), S (380-440V 50 / 60Hz) and so on.
7.The rotor in the induction motor is not energized

0.75KW 1HP Y2 80M Electric motors for sale

A 3 phase AC induction motor photoed by Hordu Motor

Advantages of three phase squirrel cage Induction Motor
Some of the main advantages, why you should go for this motor include the following:
1) small and lightweight;
2) high speed and low torque operation efficiency;
3) high torque at low speed, and a wide range of speed control;
4) high reliability
5) low maintenance costs;

Conclusion

In short, the working principle of any induction motors involves stator flux and squirrel cage rotor flux .
As you can see, the 3 phase squirrel cage induction motor could achieve the electromechanical energy conversion simple and straight forward.

At Hordu, we have a range of three phase induction motors that vary in design, technology and production capacity.

For more information about Hordu induction motors, feel free to contact our team.

Further Reading
Induction motor — Source: Wikipedia
Squirrel cage rotor — Source:Wikipedia
Induction Motor | Working Principle | Types of Induction Motor — Source:electrical4u.com
Induction motors — by Chris Woodford
PRINCIPLES OF OPERATION OF SYNCHRONOUS MACHINES — by Geoff Klempner and Isidor Kerszenbaum