Induction Motor

Three phase induction motors have a very simple construction composed of a stator protected with electromagnets, and a rotor composed of conductors shorted at each end, arranged as a “squirrel cage”. They work on the basic principle of induction where a rotating electro-magnetic field it created 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 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 structure. 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 slip rings

They are free of maintenance motors unlike dc motors due to the absence of brushes, commutators and slip rings

Induction motors could be operated in polluted and explosive environments as they don’t have brushes that may cause sparks

AC Induction motors are Asynchronous Machines and therefore the rotor will not turn 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 make the induction into 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 effectively. Roboteq AC Induction controllers can 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 change.

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 desired 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.

Find this video from Learning Induction Motor Engineering for a visual illustration on how AC Induction Motors are constructed and function.