Uniform Demagnetization Fault Diagnosis of PMSM Based on Radial Air-Gap Flux Density Under Nonstationary Conditions

Permanent magnet synchronous motor (PMSM) often operates in harsh environments, such as high temperatures and intense vibrations, which could result in partial demagnetization fault or uniform demagnetization fault (UDF). Although the probability of UDF is relatively low, once it occurs, it will cause a decrease in motor efficiency and even system paralysis. In addition, the PMSM usually operates under nonstationary conditions, which could increase the difficulty in UDF diagnosis. Hence, this article proposes a UDF diagnosis method of PMSM based on radial air-gap flux density under nonstationary conditions. In this method, the d-axis magnetic network model of PMSM is established and analyzed. The fault feature for UDF is extracted from radial air-gap flux density based on the d-axis magnetic network model. By the extracted fault feature, not only UDF can be detected, but also UDF degree can be calculated. Both the simulation and experimental results validate the effectiveness of the proposed UDF diagnosis method.