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July 10, 2020

Three phase induction motors employ a 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 work on the principle of induction where a rotating electro-magnetic field it made through the use of a three-stage Induction Motor current at the stators electromagnets. Therefore induces a current inside 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 building. 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 absence of brushes, commutators and slip rings

Induction motors could be operated in polluted and explosive environments as they do not have brushes which can cause sparks

AC Induction motors are Asynchronous Devices meaning that the rotor will not convert at the exact same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator velocity is necessary to be able to create the induction in to the rotor. The difference between the two is called the slip. Slip must be kept within an optimal range in order for the motor to use efficiently. Roboteq AC Induction controllers could be configured to operate in another of three modes:

Scallar (or Volts per Hertz): an Open up loop mode where a command causes a simultaneous, fixed-ratio Frequency and Voltage modify.

Controlled Slip: a Shut Loop speed where voltage and frequency are managed to keep slip within a narrow range while running at a preferred speed.

Field Oriented Control (Vector Drive): a Closed Loop Quickness 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 on how AC Induction Motors are constructed and function.