Rotor Time Constant Estimation of Induction Motors Using Phase Responses During I-F Operations

This article proposes a method for estimating induction motors’ (IMs’) rotor time constant (RTC). An accurate estimation is needed since RTC is an essential motor parameter for high-performance operation. As the RTC changes due to magnetic saturation, the magnetic saturation of magnetizing flux is considered. The proposed method estimates the RTC during the I-F operation, which is robust to the stator resistance error, under a no-load state considering the sensorless motor drive system. This article analyzes the response of the rotor magnetic flux to the stator current in a stator current-oriented coordinate. The proposed method estimates RTC through the phase response of the rotor magnetic flux to the stator current. As a result of analyzing the method based on magnitude and phase responses, the method based on phase response is more robust against errors of motor parameters in the proposed algorithm. The proposed method is verified through computer simulation and experiment with 3.7 and 11 kW IMs.