Three phase induction Induction Motor 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 theory of induction in which a rotating electro-magnetic field it created through the use of a three-phase current at the stators electromagnets. Therefore induces a current in the rotor’s conductors, which in turns generates rotor’s magnetic field that attempts 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 better quality and can operate in any environmental condition
Induction motors are cheaper in cost because of simple rotor construction, absence of brushes, commutators, and slide rings
They are maintenance free motors unlike dc motors due to the absence of brushes, 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 does not change at the specific same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator swiftness is necessary in order to create 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 use efficiently. Roboteq AC Induction controllers can be configured to operate in one of three modes:
Scallar (or Volts per Hertz): an Open loop mode where a command 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 running at a desired 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.
Observe this video from Learning Engineering for a visual illustration about how AC Induction Motors are constructed and work.