An induction motor (also known as an asynchronous motor) is a commonly used AC electric motor. In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. The rotor of an induction motor can be a squirrel cage rotor or wound type rotor.
Induction motors are referred to as ‘asynchronous motors’ because they operate at a speed less than their synchronous speed. So the first thing to understand is – what is synchronous speed?
Synchronous Speed
Synchronous speed is the speed of rotation of the magnetic field in a rotary machine, and it depends upon the frequency and number poles of the machine. The induction motor always runs at speed less than its synchronous speed.
The rotating magnetic field produced in the stator will create flux in the rotor, hence causing the rotor to rotate. Due to the lag between the flux current in the rotor and the flux current in the stator, the rotor will never reach its rotating magnetic field speed (i.e. the synchronous speed).
There are basically two types of induction motor. The types of induction motor depend upon the input supply. There are single phase induction motors and three phase induction motors. Single phase induction motors are not a self-starting motor, and three phase induction motor are a self-starting motor.
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