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 work on the Induction Motor principle of induction where a rotating electro-magnetic field it made 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 produces rotor’s magnetic field that attempts to check out stator’s magnetic field, pulling the rotor into rotation.

Benefits of AC Induction Motors are:

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

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

They are maintenance free 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 Machines and therefore the rotor does not change at the exact same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator velocity is necessary in order to develop the induction into the rotor. The difference between the two is called the slip. Slip must be kept in a 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 up loop mode where a order 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 inside a narrow range while running at a desired speed.

Field Oriented Control (Vector Drive): a Closed Loop Acceleration 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 function.