A new test method for estimating rotor resistance of induction motors utilizing a dynamometer

In indirect vector control, primarily utilized in induction motor (IM) vector control, accurate estimation of rotor resistance (Rr) is crucial for achieving high-performance torque and flux control. Rr estimation methods can be broadly classified into online methods, which estimate in real-time during operation, and offline methods, which provide an initial value for vector control. The purpose of real-time estimation methods is to compensate for Rr variations, mainly due to changes in rotor temperature during operation, while Rr estimated by offline methods facilitates vector control and the construction of a current reference map through a current sweep test in the d-q coordinate during the early stages of the test procedure. Although various studies have focused on online estimation methods, notable offline estimation methods beyond locked-rotor and no-load tests compliant with IEEE Std. 112 are lacking. Since Rr estimated from conventional tests may incur non-negligible errors, an improved Rr estimation method with higher accuracy is necessary. In this study, a new Rr estimation method using a dynamometer was proposed. The proposed method operates on the principle that the highest torque is generated when operating at Maximum Torque Per Ampere (MTPA) with indirect vector control only when Rr is accurately estimated. It was verified that the Rr estimated through the new method exhibited higher accuracy than the conventional method.