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 focus on the theory of induction where a rotating electro-magnetic field it created by applying a three-stage current at the stators electromagnets. This in turn induces a current inside the rotor’s conductors, which in turns generates rotor’s magnetic field that attempts 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 construction. They are more robust and can operate in virtually any environmental condition
Induction motors are cheaper in cost due to simple rotor construction, lack of brushes, commutators, and slip rings
They are maintenance free 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 do not have Induction Motor brushes which can cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor does not switch at the specific same speed because the stator’s rotating magnetic field. Some difference in the rotor and stator speed is necessary in order to develop the induction into the rotor. The difference between your two is 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 where a order causes a simultaneous, fixed-ratio Frequency and Voltage alter.
Controlled Slip: a Shut Loop speed where voltage and frequency are controlled to keep slip within a narrow range while working at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Acceleration and Torque control that functions 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.