Three phase induction motors employ a simple construction composed 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 principle of induction in which a rotating electro-magnetic field it created by applying a three-phase current at the stators electromagnets. This in turn induces a current in the rotor’s conductors, which in turns creates rotor’s magnetic field that tries to check out stator’s magnetic field, pulling the rotor into Induction Motor rotation.
Great things about AC Induction Motors are:
Induction motors are simple and rugged in structure. They are more robust and can operate in virtually any environmental condition
Induction motors are cheaper in cost due to simple rotor construction, absence of brushes, commutators, and slip rings
They are free of maintenance motors unlike dc motors due to the absence of brushes, commutators and slip rings
Induction motors could be operated in polluted and explosive environments as they don’t have brushes that may cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor does not turn at the precise same speed because 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 in a optimal range in order for the motor to use efficiently. Roboteq AC Induction controllers can be configured to operate in one of three modes:
Scallar (or Volts per Hertz): an Open loop mode where a command causes a simultaneous, fixed-ratio Frequency and Voltage alter.
Controlled Slip: a Closed 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 Rate 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 on how AC Induction Motors are constructed and function.