Three phase induction Induction Motor china Motors have a very simple construction made up 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 principle of induction where a rotating electro-magnetic field it created 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 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 structure. They are better quality and can operate in any environmental condition
Induction motors are cheaper in expense due to simple rotor construction, absence of brushes, commutators, and slide rings
They are maintenance free motors unlike dc motors because of 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 will not change at the specific same speed as the stator’s rotating magnetic field. Some difference in the rotor and stator speed is necessary in order to produce the induction in to the rotor. The difference between your two is called the slip. Slip must be kept within an optimal range to ensure that the motor to use 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 control causes a simultaneous, fixed-ratio Frequency and Voltage change.
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 Swiftness and Torque control that functions by optimizing the rotating field of the stator vs. this of the induced field in the rotor.
Observe this video from Learning Engineering for a visual illustration about how AC Induction Motors are constructed and function.