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 basic principle of induction in which a rotating electro-magnetic field it developed through the use of a three-stage current at the stators electromagnets. Therefore induces a current within the rotor’s conductors, which in turns generates 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 simple and rugged in building. They are better quality and can operate in virtually any environmental condition
Induction motors are cheaper in expense due to simple rotor construction, absence of brushes, commutators, and slip rings
They are free of maintenance 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 don’t have brushes that may cause sparks
AC Induction motors are Asynchronous Machines and therefore the rotor will not switch 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 make the induction into the rotor. The difference between your two is Induction Motor called the slip. Slip should be kept within an optimal range to ensure that the motor to use effectively. Roboteq AC Induction controllers could be configured to operate in another of three modes:
Scallar (or Volts per Hertz): an Open loop mode in which a command causes a simultaneous, fixed-ratio Frequency and Voltage change.
Controlled Slip: a Closed Loop speed where voltage and frequency are controlled to keep slip inside a narrow range while running at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Velocity 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.