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 created through the use of a three-stage current at the stators electromagnets. This in turn induces a current within the rotor’s conductors, which in turns generates rotor’s magnetic field that tries to check out stator’s magnetic field, pulling the rotor into rotation.
Benefits of AC Induction Motors are:
Induction motors are basic and rugged in structure. They are more robust and can operate in virtually any environmental condition
Induction motors are cheaper in cost because of simple rotor construction, absence of brushes, commutators, and slip rings
They are free of maintenance 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 that may cause sparks
AC Induction motors are Asynchronous Machines and therefore the rotor does not switch at the exact same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator rate is necessary to be able to create the induction in to the rotor. The difference between your two is named the slip. Slip Induction in Motor should be kept within an optimal range in order for the motor to operate efficiently. Roboteq AC Induction controllers can be configured to operate in another of three modes:
Scallar (or Volts per Hertz): an Open loop mode where a order causes a simultaneous, fixed-ratio Frequency and Voltage alter.
Controlled Slip: a Shut Loop speed where voltage and frequency are controlled in order to keep slip within a narrow range while running at a preferred 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.
Discover this video from Learning Engineering for a visual illustration on how AC Induction Motors are constructed and work.