Generally, Induction motors work on the principle of electromagnetic effect. When current supply to the coil of the induction motor. The flux is produced in the conductor of the coil. When the current-carrying conductor place in the electromagnetic field cuts the magnetic flux, the Electromagnetic motive force is produced. According to magnetizing and demagnetizing effect, the coil is rotated in the direction of the rotating magnetic field. And also induction motor is rotating.
Mainly, the induction motor has two major components it has a stator and a rotor. The stator is in a steady position, and the rotor is in a rotating condition. When current is supplied to the stator of the 3 phase induction motor, the rotating flux is produced in the stator, and the rotor is cut the magnetic flux produced by the stator. So the rotor is rotated according to the rotating magnetic flux and its direction, so 3 phase induction motor is run without any starter.
Induction motors are generally are two types, synchronous and asynchronous motors. An induction motor or asynchronous motor is an Ac Electric Motor. The electric current in the rotor needed to produce torque is obtained by Electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor. An induction motor's rotor can be either wound type or squirrel-cage type.
In both induction and synchronous, the AC power supplied to the motor's stator creates a magnetic field that rotates in synchronism with the AC oscillations. Whereas a synchronous motor's rotor turns at the same rate as the stator field, an induction motor's rotor rotates at a somewhat slower speed than the stator field. The induction motor stator's magnetic field is therefore changing or rotating relative to the rotor. This induces an opposing current in the induction motor's rotor, affecting the motor's secondary winding when the latter is short-circuited or closed through an external impedance. The rotating magnetic flux induces currents in the rotor's windings like currents induced in a transformer's secondary winding(s).
The induced currents in the rotor windings, in turn, create magnetic fields in the rotor that react against the stator field. The direction of the magnetic field created will be to oppose the change in current through the rotor windings, in agreement with Lenz lows. The cause of induced current in the rotor windings is the rotating stator magnetic field. To oppose the change in rotor-winding currents, the rotor will rotate in the direction of the rotating stator magnetic field. The rotor accelerates until the magnitude of induced rotor current and torque balances the applied mechanical load on the rotor rotation. Since rotation at synchronous speed would result in no induced rotor current, an induction motor always operates slightly slower than synchronous speed. The difference, or "slip," between actual and synchronous speed varies from about 0.5% to 5.0% for standard Design B torque curve induction motors. The induction motor's essential character is created solely by induction instead of being separately excited as in synchronous or DC machines or being self-magnetized as in permanent magnet motor.]
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