Three phase induction motors have a very simple construction composed of a stator protected with electromagnets, and a rotor composed of conductors shorted at each end, arranged as a “squirrel cage”. They focus on the principle of induction in which a rotating electro-Induction Motor china magnetic field it made by applying a three-stage current at the stators electromagnets. This in turn induces a current inside the rotor’s conductors, which in turns generates rotor’s magnetic field that tries to follow stator’s magnetic field, pulling the rotor into rotation.

Benefits of AC Induction Motors are:

Induction motors are simple and rugged in building. They are more robust and can operate in virtually any environmental condition

Induction motors are cheaper in expense due to simple rotor construction, absence of brushes, commutators, and slip rings

They are free of maintenance motors unlike dc motors due to the lack of brushes, commutators and slip rings

Induction motors could be operated in polluted and explosive conditions as they do not have brushes which can cause sparks

AC Induction motors are Asynchronous Devices and therefore the rotor will not turn at the exact same speed as the stator’s rotating magnetic field. Some difference in the rotor and stator speed is necessary in order to develop the induction into the rotor. The difference between the two is named the slip. Slip must be kept within an optimal range in order for the motor to operate efficiently. Roboteq AC Induction controllers can be configured to operate in another of three modes:

Scallar (or Volts per Hertz): an Open loop mode in which a control causes a simultaneous, fixed-ratio Frequency and Voltage change.

Controlled Slip: a Closed Loop speed where voltage and frequency are controlled in order to keep slip within a narrow range while operating at a preferred speed.

Field Oriented Control (Vector Drive): a Closed Loop Velocity and Torque control that works by optimizing the rotating field of the stator vs. this of the induced field in the rotor.

Find this video from Learning Engineering for a visual illustration about how AC Induction Motors are constructed and work.