Three phase induction motors have a very simple construction composed of a stator covered with electromagnets, and a rotor made up of conductors Induction Motor shorted at each end, arranged as a “squirrel cage”. They focus on the basic principle of induction in which a rotating electro-magnetic field it created through the use of a three-phase current at the stators electromagnets. This in turn induces a current in the rotor’s conductors, which in turns creates rotor’s magnetic field that tries to check out stator’s magnetic field, pulling the rotor into rotation.
Great things about AC Induction Motors are:
Induction motors are simple and rugged in structure. They are better quality 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 absence of brushes, commutators and slip rings
Induction motors could be operated in polluted and explosive environments as they don’t have brushes which can cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor will not turn at the specific same speed as the stator’s rotating magnetic field. Some difference in the rotor and stator quickness is necessary in order to produce the induction into the rotor. The difference between the two is named the slip. Slip should be kept within an optimal range in order for the motor to operate effectively. Roboteq AC Induction controllers could be configured to operate in one of three modes:
Scallar (or Volts per Hertz): an Open loop mode in which a command causes a simultaneous, fixed-ratio Frequency and Voltage modify.
Controlled Slip: a Shut Loop speed where voltage and frequency are controlled to keep slip inside a narrow range while working at a preferred speed.
Field Oriented Control (Vector Drive): a Closed Loop Quickness and Torque control that functions 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 about how AC Induction Motors are constructed and work.