Three phase induction motors have a very simple construction composed of a stator covered with electromagnets, and a rotor composed of conductors shorted at each end, arranged as a “squirrel cage”. They focus on the principle of induction in which a rotating electro-magnetic field it developed by applying a three-phase current at the stators electromagnets. Therefore induces a current inside the rotor’s conductors, which in turns generates 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 more robust and can operate in 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 do not have brushes which can cause sparks
AC Induction motors are Asynchronous Machines and therefore the rotor does not turn at the precise same speed because the stator’s rotating magnetic field. Some difference in the rotor and stator velocity is necessary in order to make the induction in to the rotor. The difference between your two is called the slip. Slip must be kept within an optimal range in order for the motor to operate efficiently. Roboteq AC Induction controllers can be configured to operate in one of three modes:
Scallar (or Volts per Hertz): an Open up loop mode where a command causes a simultaneous, fixed-ratio Frequency and Voltage Induction Motor china modify.
Controlled Slip: a Closed Loop speed where voltage and frequency are controlled in order to keep slip inside a narrow range while running at a preferred 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.
See this video from Learning Engineering for a visual illustration about how AC Induction Motors are constructed and work.