Three phase induction motors have a very simple construction composed of a stator protected with electromagnets, and a rotor made up of conductors shorted at each end, Induction Motor arranged as a “squirrel cage”. They work on the principle of induction where a rotating electro-magnetic field it made by applying a three-stage current at the stators electromagnets. Therefore induces a current within the rotor’s conductors, which in turns produces rotor’s magnetic field that attempts to follow stator’s magnetic field, pulling the rotor into rotation.
Benefits of AC Induction Motors are:
Induction motors are basic and rugged in construction. They are more robust and can operate in any environmental condition
Induction motors are cheaper in cost because of simple rotor construction, lack of brushes, commutators, and slip rings
They are free of maintenance motors unlike dc motors because of the absence of brushes, commutators and slip rings
Induction motors could be operated in polluted and explosive environments as they don’t have brushes which can cause sparks
AC Induction motors are Asynchronous Machines meaning that the rotor does not convert at the exact same speed as the stator’s rotating magnetic field. Some difference in the rotor and stator swiftness is necessary in order to generate the induction in to the rotor. The difference between your two is named the slip. Slip must be kept within an optimal range to ensure that the motor to use effectively. 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 modify.
Controlled Slip: a Shut Loop speed where voltage and frequency are controlled to keep slip within a narrow range while operating at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Rate and Torque control that works by optimizing the rotating field of the stator vs. this of the induced field in the rotor.
See this video from Learning Engineering for a visual illustration on how AC Induction Motors are constructed and work.