Induction motor works on principle of faraday’s law of […]
Induction motor works on principle of faraday’s law of electromagnetic induction.
It works on the principle of electromagnetic induction. When a rotor (an insulated short circuited cylindrical conductor, usually copper) is placed between an alternating magnetic field, it rotates due to a repulsive action which produces the mechanical effect. The magnetic field is provided by an energized laminated copper cylinder. The ceiling fan works on the same principle. The speciality of an induction motor is that it doesn't require any additional start up mechanism like an ordinary DC motor.
When three phase blance supply is applied on three phase symetfically placed winding, it will create rotating magnetic field. This rotating magnetic field cuts the rotor conducter so emf is induced in rotor conductor. If rotor winding is closed then current will flow through rotor wdg. According to Lenz law this current will oppose the cause which produced it so current will oppose flux cutting action and prodeuced a torque which will rotate the rotor in same dirsction of rotation of stator flux.
When speed of rotor becomes synchronous speed thwn no flux cuts through eotor co ductor. No emf induce. No current in rotor conductor. No opposition of fux cutting. No torque produced. So motor wants to stop. And as speed of motor decrease from syncheonous speed then again flux cutting action start. Again inducef emf in rotor. Again current. Again torque. So induction motor remain rotate less than synchronous speed.