Rotor Bar Fault Diagnosis in Dynamic Variable Speed Operation of Squirrel Cage Motors Using Ansys Co-Simulation and RELAX Algorithm

The traditional rotor fault diagnosis method for asynchronous motors operating at a constant speed, based on Motor Current Signature Analysis (MCSA), is often significantly influenced by strong fundamental sideband interference and load fluctuations. In practice, motors frequently operate at variable speeds, and the time-varying nature of the rotor speed and slip rate results in fault characteristics that are not constant frequency components. Hence, conventional approaches are not suitable. To address this issue, this study focuses on the startup process, which exhibits the widest range of frequency variations. Ansys is used for co-simulation of the startup process of a squirrel cage motor under rotor bar fault conditions. The Relax algorithm is employed to eliminate the influence of the fundamental frequency during the startup process. Subsequently, Continuous Wavelet Transform (CWT) is applied to extract the fault time-frequency map, and energy measurement is performed to achieve fault identification and quantification of fault severity during variable speed operation. Simulation results demonstrate the effectiveness and accuracy of this method.