An induction motor is an electric motor that operates o […]
An induction motor is an electric motor that operates on the principle of Induction. There are two parts of an induction motor i.e, Stator and Rotor. Stator is the stationary part while rotor is free to rotate. Both of these are separated by an air gap and has no connection mechanically but only coupled magnetically thus having frictionless operation unlike brushed DC motors.
The stator carries conductors through which when the alternating current (AC) i.e, time-varying current passes, produces a time-varying magnetic field. This field is cut by the rotor conductors and by laws of electromagnetic induction, emf is induced in the rotor conductors. As the rotor conductors are short circuited, the induced emf causes a current to flow through the rotor conductors which causes production of rotor magnetic field flux. These two fluxes, the stator or air gap flux and rotor flux react with each other thus producing a resultant flux which forces the rotor to rotate. This is how an induction motor works.
It can also be explained in this way. The rotor induced emf is so as to oppose the very cause of its own creation (Lenz's law of electromagnetic induction) i.e, the rotor induced emf opposes the stator air gap flux and hence the rotor being free to move, begins rotation tending to be inline with the stator field flux so that it doesn't have to cut it and thus reduce thus effect i.e, induced emf. As the air gap flux is rotating (3 phase air gap flux are rotating in nature which can be shown in mathematical analysis), the rotor begins rotation in order to achieve stability but falls behind due to inertia and load on it.