Three phase induction motors employ a simple construction made up of a stator covered with electromagnets, and a rotor made up of Induction Motor china conductors shorted at each end, arranged as a “squirrel cage”. They focus on the basic principle of induction where a rotating electro-magnetic field it developed through the use of a three-phase current at the stators electromagnets. Therefore induces a current within the rotor’s conductors, which in turns generates rotor’s magnetic field that tries to follow stator’s magnetic field, pulling the rotor into rotation.
Benefits of AC Induction Motors are:
Induction motors are simple and rugged in construction. They are more robust and can operate in virtually any environmental condition
Induction motors are cheaper in cost due to simple rotor construction, absence of brushes, commutators, and slip rings
They are maintenance free motors unlike dc motors due to the lack of brushes, commutators and slip rings
Induction motors can be operated in polluted and explosive conditions as they don’t have brushes that may cause sparks
AC Induction motors are Asynchronous Machines and therefore the rotor will not change at the precise same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator rate is necessary in order to produce the induction in to the rotor. The difference between the two is named 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 another of three modes:
Scallar (or Volts per Hertz): an Open loop mode where a command 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 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.
Discover this video from Learning Engineering for a visual illustration about how AC Induction Motors are constructed and function.