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 work on the basic principle of induction where a rotating electro-magnetic field it made by applying a three-stage current at the stators electromagnets. This in turn induces a current within the rotor’s conductors, which in turns produces rotor’s magnetic field that attempts to follow 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 expense due to simple rotor construction, lack 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 conditions as they don’t have brushes which can cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor does not convert at the precise same speed because the stator’s rotating magnetic field. Some difference in the rotor and stator rate is necessary in order to generate 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 use efficiently. 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 order causes a simultaneous, fixed-ratio Frequency and Voltage alter.
Induction Motor controlled Slip: a Shut Loop speed where voltage and frequency are controlled to keep slip inside a narrow range while operating 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.
Discover this video from Learning Engineering for a visual illustration on how AC Induction Motors are constructed and work.