Three phase induction motors employ a 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 where a rotating electro-magnetic field it created by applying a three-phase current at the stators electromagnets. Therefore induces a current inside the rotor’s conductors, which in turns creates rotor’s magnetic field that attempts to check out stator’s magnetic field, pulling the rotor into rotation.

Great things about AC Induction Motors are:

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

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

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

Induction motors could be operated in polluted and explosive conditions as they don’t have brushes which can cause sparks

AC Induction motors are Asynchronous Devices and therefore the rotor does not switch at the exact same speed as the stator’s rotating magnetic field. Some difference in the rotor and stator velocity is necessary to be able to create the induction into the rotor. The difference between the two is called the slip. Slip should be kept within an optimal range to ensure that the motor to operate efficiently. Roboteq AC Induction controllers could be configured to operate in one of three modes:

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

Controlled Slip: a Shut Loop speed where voltage and frequency are managed in order to keep slip inside a narrow range while running at a desired speed.

Field Oriented Control (Vector Drive): a Closed Loop Acceleration and Torque control that functions 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 function.