What is the working principle of 3φ induction motor?

What is the working principle of 3φ induction motor?
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1 Answer

Answer :

When 3φ supply is given to stator, a rotating magnetic field of constant magnitude is produced. This rotating magnetic field produces induced emf in the rotor winding as per faraday’s laws and this induced emf causes to circulate a heavy induced current in the rotor winding due to very small resistance of rotor. At the initial moment the frequency of induced emf is equal to the frequency of the stator supply voltage, when the rotor is stationary as in the case of secondary of a transformer. The rotor induced current according to lenz’s law flows in such a direction that it opposes the cause, which is inducing it. In this case the cause producing the rotor current is the relative speed between the rotating magnetic field if stator and the rotor and is maximum when the rotor is stationary. Hence to reduce this relative speed rotor conductor (rotor) starts to rotate in the same direction in which the stator field is rotating and tries to catch it up. The rotation of this rotor is developed due tog the torque developed in the rotor by interaction between the rotating magnetic field of stator and the field produced by the rotor current.
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