Unified formulation for rotor-flux estimation in an induction motor

This paper shows that any rotor flux estimator can be analysed, in steady state, combining two basic estimators: the current and the voltage models. This formulation can be used to investigate the internal structure and robustness of any estimator as a function of the motor operating point. In addition, a design method for a rotor-flux estimator is proposed based on this formulation. This method is illustrated with a simple example. The estimator obtained is compared by simulation with a reduced-order observer when both estimators are used in a direct field-oriented control