Three phase induction motors employ a simple construction made up of a stator covered with electromagnets, and a rotor made up of conductors shorted at each end, arranged as a “squirrel cage”. They work on the basic principle of induction where a rotating electro-magnetic field it developed through the use of a three-phase current at the stators electromagnets. This in turn 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 basic and rugged in building. They are more robust and can operate in any environmental condition

Induction motors are cheaper in cost because of simple rotor construction, absence of brushes, commutators, and slide rings

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

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

AC Induction motors are Asynchronous Devices and therefore the rotor will not convert at the precise same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator speed is necessary to be able to make the induction into the rotor. The difference between the two is named the slip. Slip must be kept within an optimal range to ensure that the motor to operate effectively. Roboteq AC Induction controllers can be configured to operate in one of three modes:

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

Induction in Motor 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 Velocity and Torque control that works by optimizing the rotating field of the stator vs. this of the induced field in the rotor.

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