Induction Motor Rotating Transformer Relation

Relation between Transformer and Induction Motor:

Induction motor and Electrical Transformer operates on the same Faraday's law of electro-magnetic induction principle. 

In Electrical Transformer when voltage is applied to the primary winding, it draws magnetising current and load current. Magnetizing current is required to magnetize the core of the lamination. This magnetizing current produces flux which travels to the secondary winding of the transformer and completes the closed loop back to the primary winding through the magnetic core of the transformer

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In Induction motor there is no electrical connection to the rotor. When a 3-phase voltage applied to the stator winding it produces a rotating magnetic field which rotates at synchronous speed. When the flux cuts the stationary rotor conductors an emf is induced similar to the emf induced in the secondary side of the transformer. As the rotor winding of the induction motor is short circuited (Closed) current flows through the rotor which sets up the torque of the rotor. 

The main difference between the electrical transformer and induction motor is in electrical transformer magnetic path is a closed one through the core of the transformer. On the other hand, in induction motor air gap present between the stator and rotor windings. For obtaining electro-mechanical conversion air gap is required. Thus Induction motors are considered as rotating transformers