Shaft Trajectory Analysis in a Partially Demagnetized Permanent-Magnet Synchronous Motor

Abstract

Demagnetization faults have a negative impact on the behavior of permanent-magnet synchronous machines, thus reducing their efficiency, generating torque ripple, mechanical vibrations, and acoustic noise, among others. In this paper, the displacement of the shaft trajectory induced by demagnetization faults is studied. It is proved that such faults may increase considerably the amplitude of the rotor displacement. The direct measure of the shaft trajectory is performed by means of a noncontact self-mixing interferometric sensor. In addition, the new harmonics in the back electromotive force (EMF) and the stator current spectrum arising from the shaft displacement are analyzed by means of finite-element method (FEM) simulations and experimental tests. Since conventional finite-element electromagnetic models are unable to predict the harmonics arising from the shaft trajectory displacement, an improved finite-element model which takes into account the measured trajectory has been developed. It is shown that this improved model allows obtaining more accurate back EMF and stator current spectra than those obtained by means of conventional models. This work presents a comprehensive analysis of the effects generated by demagnetization faults, which may be useful to develop improved fault diagnosis schemes.

Advances in Electrical Machine, Power Electronic, and Drive Condition Monitoring and Fault Detection: State of the Art

“…Obviously, approaches proposed in [67], [68] require accurate information of the behavior of the machine in healthy condition. In [69], the authors propose a finite element model which takes into account the motor shaft displacement due to the unbalanced magnetic forces that partial demagnetization produces. This improved model gives a more realistic simulation of the currents than conventional FEM models.…”

Analysis of Vibrations in Interior Permanent Magnet Synchronous Motors Considering Air-Gap Deformation

“…However, for the PMSM applied in an in-wheel motor driving system, the manufacture tolerance, the assembly quality, the demagnetization faults [11], the operating conditions and the performing environments can all lead to stator and rotor core deformations and eccentricities, which are called air-gap deformation. In order to reduce the vibration of the IPMSM, the mathematical correlation between air-gap deformation and electromagnetic vibration should be analyzed.…”

Detection of Partial Demagnetization Fault in PMSMs Operating Under Nonstationary Conditions

“…Thus, early and accurate detection of the partial demagnetization fault is of great significance for the operation & maintenance of PMSMs and associated machinery and electromechanical systems. So far, the commonly monitored parameters for Partial Demagnetization Fault Detection (PDFD) are stator current [3][4][5], zero sequence voltage component [6], Back-EMF [7], shaft trajectory [8] and vibration [9]. Following the classical motor current signature analysis approach, the characteristic demagnetization fault frequencies, fd, are 1 , where f0 is the electrical fundamental frequency, k is an integer, and is the number of pole pairs [3][4][5][6][7][8][10][11][13][14].…”

“…So far, the commonly monitored parameters for Partial Demagnetization Fault Detection (PDFD) are stator current [3][4][5], zero sequence voltage component [6], Back-EMF [7], shaft trajectory [8] and vibration [9]. Following the classical motor current signature analysis approach, the characteristic demagnetization fault frequencies, fd, are 1 , where f0 is the electrical fundamental frequency, k is an integer, and is the number of pole pairs [3][4][5][6][7][8][10][11][13][14]. Thus, the PDFD under stationary conditions of speed and torque is commonly based on the identification of such characteristic fault frequencies throughout the spectrum analysis, estimated by means of conventional Fourier Analysis (FA) [6][7][8].…”

“…Following the classical motor current signature analysis approach, the characteristic demagnetization fault frequencies, fd, are 1 , where f0 is the electrical fundamental frequency, k is an integer, and is the number of pole pairs [3][4][5][6][7][8][10][11][13][14]. Thus, the PDFD under stationary conditions of speed and torque is commonly based on the identification of such characteristic fault frequencies throughout the spectrum analysis, estimated by means of conventional Fourier Analysis (FA) [6][7][8]. All frequency components of the analyzed signal could be revealed via FA, which is only suitable for analysis under stationary conditions, the frequencies changing with time could not be tracked.…”