Rotor time constant identification for vector controlled induction motor drives under dynamic operating conditions

The dynamic performance of an indirect vector controlled induction motor drive requires a good knowledge of the motor parameters. For the scheme based on rotor position measurement and inner current loops, the rotor time constant (T_r) is the most influential time varying parameter. In this study an extension of the reactive identification scheme is presented and it is shown that the scheme can track the motor time constant during both dynamic torque and dynamic flux conditions. The scheme is used in conjunction with a rotor flux orientated controller. Problems such as the variation of mutual inductance with flux level and digital conversion and calculation inaccuracy when noise is present on the measurement values are discussed. Simulation studies show that the method follows T_r correctly under all operating conditions with a good accuracy.