EWT Implementation for Examining Demagnetization Fault in PMSM using FEM *

Abstract

The goal of this work is to examine the demagnetization fault in a surface-mounted permanent magnet synchronous motor (PMSM) utilizing the finite element method (FEM) and to investigate motor current by employing empirical wavelet transform (EWT). Detection of demagnetization fault at the beginning level is critical in PMSM fault diagnosis. Due to the high cost of permanent magnets and to avoid the destruction of the machine, it is necessary to detect the fault at the earliest. In this context, a 550 W surface-mounted PMSM in ANSYS Maxwell finite element tool is proposed for investigation. Demagnetization fault is included in the PMSM model by varying the permanent magnet material coercivity. The analysis considers various fault severity levels such as 1 %, 2%, 5%, and 10% of demagnetization. Electromagnetic features such as stator current and dissemination of flux inside the motor are analyzed and correlated with a healthy motor. Reduction in phase current magnitudes is noticed even for 1 % demagnetization. Spatial FFT of flux density in the airgap (radial) shows a decrease in peak amplitude when the fault severity increases. EWT in MATLAB is utilized to examine the motor current acquired from the healthy and demagnetized finite element PMSM model. The analysis exhibits a decrease in amplitudes of phase current decomposed elements in specific frequency band based on fault severity compared to the healthy motor.