An inside look at cage motors with vector control

The authors present a simple picture of the mechanism of precise torque control of a cage induction motor from the viewpoint of the electrical machines engineer. They focus attention on how and why the stator currents must be controlled in order to control instantaneous torque, and show in particular how the stator currents must be varied to obtain sudden step increases in torque. It turns out that the conditions are quite simple, and that they can be quantified in terms of only two parameters. Understanding the `inside workings´ of the motor at this basic level is helpful in stripping away some of the mystique surrounding vector control