Local Demagnetization Fault Diagnosis for Short-Primary Permanent Magnet Synchronous Linear Motor Using Two Toroidal-Yoke-Type Search Coils

Local demagnetization fault (LDF) in a short-primary permanent magnet synchronous linear motor (SP-PMSLM) degrades performance and efficiency. Demagnetization fault diagnosis can improve the reliability and stability of SP-PMSLM. Thus, this paper proposes an LDF diagnosis method based on the residual voltage difference of two toroidal-yoke-type search coils (TYT-SCs). First, the healthy and demagnetized finite element models of the SP-PMSLM are constructed using Magnet software. Second, port residual voltages of three TYT-SCs located at different locations are analyzed. Through the analysis, the residual voltage difference of two TYT-SCs mounted on the side of the primary iron core is used to remove the end effects of SP-PMSLM and diagnose demagnetization faults. Third, the acquisition method of healthy port voltage under complicated operating conditions is introduced. Finally, local demagnetization fault detection and severity assessment is completed by calculating the integral area (IA) of each half-periodic cycle. The simulation results demonstrate the effectiveness of this diagnostic method.