Field weakening of induction motors in a very wide region with regard to parameter uncertainties

In this paper, a new approach to induction machine control is presented that ensures the production of maximum torque over the permitted speed range. In the first part of the paper the steady state torque capability of an induction motor with saturation air gap inductance is analysed, when voltage as well as current are limited. This maximum torque can be achieved with different control schemes. Nevertheless, the schemes differ in view of robustness and the requirements to reach the optimum. In this paper, a scheme is presented that achieves the optimum operating point in the whole field weakening region only by means of the measured values of voltage and current. This method guarantees a robust adjustment with regard to the parameter uncertainties and the variable DC link voltage