A Less-Invasive Method for Accurately Diagnosing Demagnetization Fault in PMSM Using Rotor Partition

This article presents a less-invasive method for accurately diagnosing demagnetization fault in permanent magnet synchronous motors (PMSMs) using rotor partition. The rotor permanent magnets (PMs) are partitioned according to certain rules. The PMs condition of each partition is sequentially diagnosed through the signals measured by two additional toroidal yoke coils; thus, the conditions of all rotor PMs are diagnosed. First, the working mechanism of the search coil (SC) is analyzed, and the partitioned model of SC residual voltage is also presented. Second, the relationship between residual voltage signatures of SC and different demagnetization fault modes is studied by the established model. From the analysis, a demagnetization fault location method is proposed. The simulation and experimental results validate the correctness of the proposed method and indicate the proposed fault location method applies to the online diagnosis of both local and uniform demagnetization faults. In addition, the location of demagnetized PMs can be detected under any demagnetization fault condition and is not affected by other fault signals. Finally, a comparison with existing methods based on SC is performed and indicates the proposed method can locate faults more quickly and accurately than that of existing methods when the PM is demagnetized by 10%, and it is less invasive, especially has advantages in locating demagnetization PMs in PMSM with numerous pole-pairs. This article provides a new idea for the demagnetization fault location of PMSM, as well as provides a significant reference for a motor maintenance schedule and fault-tolerant control of PMSM.