Three phase induction motors have a very simple construction made up of a stator covered with electromagnets, and a rotor made up of Induction Motor 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 by applying 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 attempts to check out stator’s magnetic field, pulling the rotor into rotation.
Benefits of AC Induction Motors are:
Induction motors are basic and rugged in building. They are better quality and can operate in any environmental condition
Induction motors are cheaper in cost because of simple rotor construction, lack of brushes, commutators, and slide rings
They are maintenance free motors unlike dc motors because of the lack of brushes, commutators and slip rings
Induction motors can be operated in polluted and explosive environments as they don’t have brushes that may cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor will not convert at the exact same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator acceleration is necessary in order to generate the induction in to the rotor. The difference between the two is called the slip. Slip should be kept within an optimal range to ensure that the motor to operate effectively. Roboteq AC Induction controllers could be configured to operate in another of three modes:
Scallar (or Volts per Hertz): an Open up loop mode in which a order causes a simultaneous, fixed-ratio Frequency and Voltage alter.
Controlled Slip: a Closed Loop speed where voltage and frequency are managed in order to keep slip within a narrow range while running at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Swiftness and Torque control that functions 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 on how AC Induction Motors are constructed and work.