Three phase induction motors have a very simple construction made up of a Induction Motor stator covered with electromagnets, and a rotor made up of conductors shorted at each end, arranged as a “squirrel cage”. They work on the basic principle of induction where a rotating electro-magnetic field it created by applying a three-phase current at the stators electromagnets. This in turn induces a current within the rotor’s conductors, which in turns creates rotor’s magnetic field that tries to follow 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 cost due to simple rotor construction, absence of brushes, commutators, and slide rings
They are free of maintenance motors unlike dc motors because of the absence of brushes, commutators and slip rings
Induction motors can be operated in polluted and explosive environments as they do not have brushes which can cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor does not change at the specific same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator velocity is necessary in order to create the induction in to the rotor. The difference between the two is named the slip. Slip should be kept in a optimal range in order for 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 command causes a simultaneous, fixed-ratio Frequency and Voltage change.
Controlled Slip: a Shut Loop speed where voltage and frequency are managed in order to keep slip inside a narrow range while working at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Swiftness and Torque control that works by optimizing the rotating field of the stator vs. this of the induced field in the rotor.
Find this video from Learning Engineering for a visual illustration on how AC Induction Motors are constructed and work.