Three phase induction motors have a very simple construction made up 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 basic principle of induction in which a rotating electro-magnetic field it Induction in Motor 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 creates 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 any environmental condition

Induction motors are cheaper in expense because of simple rotor construction, lack of brushes, commutators, and slide rings

They are free of maintenance motors unlike dc motors because of the absence 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 meaning that the rotor will not convert at the precise same speed because the stator’s rotating magnetic field. Some difference in the rotor and stator speed is necessary in order to develop the induction in to the rotor. The difference between the two is named the slip. Slip must be kept in a 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 modify.

Controlled Slip: a Closed Loop speed where voltage and frequency are managed in order to keep slip within a narrow range while working at a preferred speed.

Field Oriented Control (Vector Drive): a Closed Loop Rate and Torque control that functions 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 on how AC Induction Motors are constructed and function.