Online identification of the rotor time constant of an induction machine

Indirect field oriented control of an induction machine requires knowledge of the rotor time constant to estimate the rotor flux linkages. An online method is described for estimating the rotor time constant and the stator resistance both of which vary during operation of the machine due to ohmic heating. The method formulates the problem using a nonlinear least-squares criterion and is guaranteed to find the minimizing solution (parameter values) in a finite number of steps. In this work the algorithm has been implemented online in simulation with the results demonstrating its application and efficacy.