THREE PHASEINDUCTION MOTOR-PRINCIPLE CONSTRUCTION AND WORKING
The motor is a device which converts electrical energy into mechanical energy. In case of three phase ac operation. Three phase induction motor is widely used. This type of motor does not require any devices for starting. These type of motor are self-starting. This type of motors are single excited AC machine. In these type of motors the supply is directly connected to the stator and rotor receives energy from stator by means of electromagnetic induction. Hence these motors are called three phase induction motor.
Three phase induction motor consists following parts:-
- Cooling fans
when stator is connected with the 3 phase AC supply, it establishes a rotating magnetic field which rotates at the Synchronous speed.
This is due to faradays law of electromagnetic induction”which states that an Emf is induced in any circuit is due rate of change of magnetic flux linkage through the circuit”.
As rotor winding is an Induction Motor are short circuited by end ring, and cut the stator rotating magnetic field. An emf is induced in the rotor copper bars and due to this Emf a current flows through the rotor conductor.
Here the relative speed between the rotating flux and the static stator rotor conductor is the cause of current generation. Hence as per Lenz law the rotor will rotate in the same direction to reduce the cause i.e the relative velocity. The rotor speed should not reach the synchronous speed produced by the stator.
If speed equals the would be no such relative speed , so no emf induced in the rotor & no current would be flowing, and therefore no torque develop would be generated. Therefore the rotor cannot reach the synchronous speed. The difference between synchronous speed and the rotor speed is called slip.
The rotation of magnetic field in an induction motor has the advantage that no electrical connections is needed in the rotor.
To buy this motor click on the link