Three phase induction motor

What is a three-phase induction motor? Different parts of a three-phase induction motor or motor parts and working principle of 3 phase induction motor A fair idea has been given. speed control methods of 3 phase induction motor and starting methods of 3 phase induction motor A brief idea has been given.

What is 3 phase induction motor?

The motor that operates based on Faraday's principle of electromagnetic induction is called an induction motor. The induction motor in which the motor is operated by supplying a three-phase supply is called a 3 phase induction motor.

This three-phase induction motor is usually used for heavy work. This type of motor is used in mill factories and industrial establishments.

3 phase induction motors require a three-phase supply that is not normally available in the home. Single-phase is used in the home.

Motor parts OR 3 phase motor parts

1. Motor frame: The frame is the heaviest part of a three-phase induction motor. The motor is mounted on the floor with two bases on either side of the frame. The stator is placed in the middle of the frame.
Stator and Rotor
2. Motor stator: The stator is an important part of the three-phase induction motor. The windings of the three-phase induction motor are placed in the stator. The power supply to these windings in the stator produces magnetic flux and the rotor rotates.

3. Motor rotor: The rotor is placed in the space between the stator of the three-phase induction motor. The magnetic flux in the rotor is absorbed by the winding of the stator.

4. motor shafts: Three-phase induction motor rotors have shafts at both ends. The motors are used by the shafts and the cooling fan is installed on the opposite side.

5. motor bearings: Ball bearings are placed on the endplate set. The rotor can easily rotate between the stator by a ball bearing.

6. Motor endplate: Endplate sets are placed with the motor frame. The endplate set protects the stator and winding from two directions.

7. Motor cooling fan: Three-phase induction motor keeps the cooling fan motor cool. Rotation of the motor causes the motor to heat up and with the help of this cooling fan, the motor is kept cool through the air.

8. Air gap motor: After setting the status and rotor, there is some air gap between the status and the rotor. This gap is called an air gap.

9. Motor terminal box: The terminal box is placed on top of the motor. Which is used to supply stator winding power.
Motor-parts-OR-3-phase-motor-parts

working principle of three-phase induction motor


Electrical motors The main function of single-phase induction motors and three-phase induction motors or any motor is to convert electrical energy into mechanical energy.

Three-phase induction motor This name implies that this motor is supplied with three-phase power. The most important part of a three-phase induction motor is the stator and rotor. The working principle of the Squirrel cage rotor type motor of a three-phase induction motor is discussed.

The winding of a three-phase induction motor is placed on the stator in such a way that it is placed 90 degrees vertically with its own winding, Which generates the North Pole and the South Pole among themselves.
In the same way, when winding, R, Y, B three-phase winding is placed 90 degrees with its own winding.
working-principle-of-three-phase-induction-motor
The type of three-phase supply supplied to a three-phase induction motor has a phase difference of 120 degrees. The coils are positioned 90 degrees apart in the stator based on the phase difference.

In this case, a three-phase supply is given to the winding in the stator. A three-phase supply generates a magnetic field in the stator coil. The magnetic field generated by the three-phase supply is a 120-degree phase difference.

From this, it can be said that the magnetic flux generated in the R phase is generated 120 degrees backward from the magnetic flux generated in the Y phase. Again the magnetic flux generated in phase Y is generated 120 degrees behind the magnetic flux generated in phase B.

A three-phase induction motor produces three rotating fields by three-phase power.

The magnetic field generated by the three-phase supply to the winding in the stator is generated by the rotary in the Northpole and Southpole ways, based on Faraday's induction principle.

The magnetic field generated in the rotor produces north pole and south poles like rotor and stator winding. The north pole generated in the rotor attracts the south pole generated in the stator. This attraction causes the motor to rotate.

Three-phase supply and three windings produce three winding Northpole and South Pole. As a result, the rotor can never hold the pole opposite the stator, and thus the rotor of the motor rotates. As a result, the three-phase induction motor is called a self-starting motor.
speed control methods of 3 phase induction motor

1. stator voltage control for the speed control of induction motor is suitable for (Control from the stator direction )
a. Changes the applied voltage
b. Changes the frequency of the actual voltage
c. Changes the number of poles in the stator

2. Control from the direction of the rotor ( slotted rotor direction )
a. The rotor controls the rheostat
b. Run two motors by cascade or concatenation
c. Applies EMF to the rotor circuit

starting methods of 3 phase induction motor

1. Squirrel cage induction motor

a. Direct Starting

b. Reduced voltage starting


Reduced voltage starting

a. Primary Resistance Reactance method

b. Auto Transformer method

c. Star-delta method


starting torque of induction motor


No current flows through the rotor coil, be it induction motor single-phase or three-phase.


Due to the effect of electromagnetic induction, the electrical pressure on the rotor coil is affected. (Much like a transformer; so the induction motor can be called a rotating transformer)


Since the rotor circuit of the induction motor is closed, current flows according to the induction principle at the rotor coil. That is why it is called an induction motor.

As a result of the application of current from the supply to the DC motor to the rotor, it can also be called a commutation motor.

The three-phase induction motor has stator three-phase winding. When supplied, it creates a rotating magnetic field and rotates at synchronous speeds.

This magnetic field line captures the voltage at the rotor conductor, which generates current and torque. The rotating magnetic field rotates here and there and starts rotating the rotor according to Lenz’s law.

However, due to friction and other energy barriers, the speed of the rotor is a little less than the synchronous speed. When the load is high, the torque increases and the speed decreases.

FAQ In Three-phase induction motor

Q1. why 3 phase induction motor is self-starting?
Ans: No additional winding is required to start the three-phase induction motor. The motor is started automatically in the welding that is done for the three-phase power supply.

Q2. What is the degree of the phase difference of a three-phase induction motor?
Ans: The phase difference of the three-phase induction motor is 120 degrees as a result of the supply of the three-phase power supply. And the coils make Northpole and South flower at 90 degrees among themselves.

Q3. What type of motor is used for a three-phase induction motor?
Ans: Three-phase induction motor Squirrel cases rotor is used. So it is also called Squirrel cases motor.

Q4. Where is the three-phase induction motor used?
Ans: Three-phase induction motors are commonly used for heavy work. It is not commonly used in the home. Used in industrial work or heavy machinery.

If you have any doudts.Please let me know

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