Three phase induction motors employ a 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 theory of induction where a rotating electro-magnetic field it produced by applying a three-stage current at the stators electromagnets. Therefore 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.
Benefits of AC Induction Motors are:
Induction motors are simple and rugged in structure. They are better quality and can operate in any environmental condition
Induction motors are cheaper in expense because of simple rotor construction, absence of brushes, commutators, and slip rings
They are free of maintenance motors unlike dc motors because of the lack of brushes, Induction Motor china commutators and slip rings
Induction motors can be operated in polluted and explosive conditions as they do not have brushes which can cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor will not switch at the precise same speed as the stator’s rotating magnetic field. Some difference in the rotor and stator swiftness is necessary to be able to make the induction into the rotor. The difference between the two is called the slip. Slip should be kept within an optimal range in order for the motor to operate efficiently. Roboteq AC Induction controllers could be configured to operate in one of three modes:
Scallar (or Volts per Hertz): an Open loop mode where a control causes a simultaneous, fixed-ratio Frequency and Voltage alter.
Controlled Slip: a Shut Loop speed where voltage and frequency are controlled in order to keep slip inside a narrow range while running at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Acceleration 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.