An accurate rotor time constant estimation method for self-commissioning of multi-scale induction motor drives

Abstract

This paper presents a novel strategy for accurate rotor time constant estimation while the induction motor keeps standstill. Based on the ‘Γ’ equivalent motor circuit model with all leakage located in the stator, the inertial first-order delay occurs in the mutual current relative to the stator current. Moreover, the delay time constant is only decided by the rotor time constant. Thus, an observer to estimate the mutual current by sample signal can be constructed. By changing the stator current at special moment according to the estimated mutual current, a significant transient response of stator voltage can be observed if estimated rotor time constant incorrect. Subsequently, a fast and robust close-loop null regulator is built to self-tune the rotor time constant. This method is completely independent of motor parameters and immune to the influence of dead time effect and voltage drop of semiconductor device. Experimental results on two different IMs are presented to prove the validity of the proposed method.