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 where a rotating electro-magnetic field it developed by applying a three-phase current at the stators electromagnets. Therefore induces a current within the rotor’s conductors, which in turns creates rotor’s magnetic field that attempts 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 more robust and can operate in any environmental condition
Induction motors are cheaper in expense due to simple rotor construction, lack 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 conditions as they do not have brushes which can cause sparks
AC Induction motors are Asynchronous Devices meaning that the rotor does not change at the exact same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator quickness is necessary to be able to develop the induction into the rotor. The difference between the two is named 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 one of three modes:
Scallar (or Volts per Hertz): an Open up loop mode where a control causes a simultaneous, fixed-ratio Frequency and Voltage modify.
Controlled Slip: a Closed Loop speed where voltage and frequency are managed to keep slip within a narrow range while working at a preferred speed.
Field Oriented Control (Vector Drive): a Closed Loop Velocity 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 Induction in Motor Engineering for a visual illustration on how AC Induction Motors are constructed and function.