Three phase induction motors employ a simple construction composed of a stator protected with electromagnets, and a rotor made up of conductors shorted at each end, arranged as a “squirrel cage”. They work on the theory of induction in which a rotating electro-magnetic field it made through the use of a three-stage current at the stators electromagnets. Therefore 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.
Great things about AC Induction Motors are:
Induction motors are basic and rugged in construction. They are better quality and can operate in virtually any environmental condition
Induction motors are cheaper in cost due to simple rotor construction, lack of brushes, commutators, and slide rings
They are maintenance free motors unlike dc motors due to the lack of brushes, commutators and slip rings
Induction motors can be operated in polluted and explosive environments as they don’t have brushes which can cause sparks
AC Induction motors are Asynchronous Devices meaning that the rotor will not turn at the specific same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator swiftness is necessary in order to develop the induction into the rotor. The difference between your two is called the slip. Slip must be kept within an optimal range in order for the motor to use Induction in Motor efficiently. Roboteq AC Induction controllers can be configured to operate in one of three modes:
Scallar (or Volts per Hertz): an Open loop mode in which a order causes a simultaneous, fixed-ratio Frequency and Voltage change.
Controlled Slip: a Closed Loop speed where voltage and frequency are managed in order to keep slip within a narrow range while operating at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Speed 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 work.