Without a doubt, 3 phase AC induction motor is the most commonly use the electrical machine in the industry. The main advantages of induction motors are. They are easier to maintain, cheaper and got rugged construction. Normally induction motor has two main parts which are stator and rotor.The stator is stationary part of the motor and the rotor is the rotating part of this motor.
Construction of 3 Phase AC Induction Motor
Stator part of this motor is created by highly permeable steel lamination inside a frame which constructs on steel or cast iron. There are several windings types and designs inside the slot of the stator.
Working Principle of Induction Motor
Three phase alternative current passes through this winding. So inside of the stator part, it creates a rotating magnetic field (rmf) inside this motor.
The speed of rotation of the magnetic field is known as synchronous speed (Ns). The rotating magnetic field of the stator induces current on the rotor part of the induction motor. So the rotor also gets the rotation.
This is the reason which this motor is so called induction motor. The motor electricity is induced in the rotor by magnetic induction.
To support magnetic induction there is insulated iron core lamina are put inside the rotor of this induction motor. Due to insulate laminar core the effect of eddy current gets reduce.
Advantage of Induction Motors
Another main advantage of 3 phase AC induction motor over other motors is, the induction motor is the self-starting motor.It can also use for most common industrial applications.
How does 3 Phase Induction Motor operate?
Consider when motor speed (rotor) same as the magnetic speed of the stator. Then the rotating loop is always same constant magnetic field due to that there are no induce emf or current will generat.
This results zero force on the rotor side of the induction motor. Due to that this reason the rotor will gradually slow down and due to this slow down the rotor loop got difference in magnetic field .
So Induced current will rise again then again the rotor will speed up. Due to that rotor unable to catch up the speed of the magnetic field or Synchronous speed of the motor.
Anyway the rotor is rotated slightly speed less than the synchronous speed of the induction motor. This difference between the synchronous speed and rotor speed is know as slip (S).
Energy loss during the motor operation is dissipated as heat energy. So normally there are fan of the other end of the induction motor to cool down this motor.
So hope that you have some good understandin on the construction working principal and the operation of the 3 phase AC induction motor.