Analytical calculation and finite element evaluation of electromagnetic leakage field distribution in surface-mounted permanent magnet synchronous motors taking the rotor eccentricity effect into account

Purpose The purpose of this paper is to present an analytical calculation for estimating the leakages field distribution in surface-mounted permanent magnet synchronous motors (SMPMSMs) according to a sub-domain field model for eccentricity fault detection. Design/methodology/approach The magnetic field domain is classified into four sub-domains of PMs, air gap, stator core and outer region. In the proposed method, the governing equations taking the rotor eccentricity effect into account per region and the interface boundary conditions between sub-domains are formulated using the regular perturbation technique, Taylor series and Fourier series expansion. Maxwell's equations are solved in different regions in the polar coordinate system regarding the boundary conditions. Findings The radial and tangential components of electromagnetic field distribution in all sub-domains of one SMPMSM are obtained using the proposed method analytically. Finite element analysis is used to validate the results of the proposed method; the results indicated that the analytical model matches the finite-element prediction up to 30% eccentricity, except for some peak values that depend on the harmonic order value. The results of this paper demonstrated that in the event of eccentricity, an asymmetric magnetic field is generated in the outer region of the machine. Although its amplitude is small, it can be an indicator for detecting eccentricity faults from the outside environment of the machine. Originality/value The formulas presented in this paper can be applied as a new technique for detecting eccentricity faults in these motors from the outside environment.

Mechanism Analysis and Optimum Control of Negative Airgap Eccentricity Effect for in-wheel Switched Reluctance Motor Driving System

This paper analyzes the generation and influence mechanism of negative airgap eccentricity effect for in-wheel switched reluctance motor (SRM) driving system, and proposes an optimum control strategy to achieve cooperative optimal performance between in-wheel motor driving system and electric vehicle (EV). Firstly, the electromagnetic characteristic of SRM under airgap eccentricity is studied based on electromagnetic coupling model and circuit driving equation. Then, the negative effect of airgap eccentricity on the in-wheel SRM driving system is analyzed in timefrequency domain combined on the excitation characteristics of unbalanced radial force. Finally, an independent current chopping control strategy for in-wheel SRM driving system based on vehicle vibration feedback is proposed, and the controller parameters are optimized by interpolation. The simulation results show that the proposed optimum control strategy can improve the driving torque while restrain the unbalanced radial force, and effectively suppress the negative airgap eccentricity effect of in-wheel motor driving system. This study starts from the dynamics relationship between SRM, in-wheel motor driving system and EV, and lays a theoretical foundation for solving the negative dynamic effect of in-wheel motor driving system.

Eccentricity Effect of Deformation Detection for Radial Frequency Patterns With Their Centers at Fixation Point

We measured the eccentricity effect of deformation thresholds of circular contours for two types of the radial frequency (RF) patterns with their centers at the fixation point: constant circular contour frequency (CCF) RF patterns and constant RF magnified (retino-cortical scaling) RF patterns. We varied the eccentricity by changing the mean radius of the RF patterns while keeping the centers of the RF patterns at the fixation point. Our peripheral stimulus presentation was distinguished from previous studies which have simply translated RF patterns at different locations in the visual field. Sensitivity for such shape discrimination fell off as the moderate and high CCF patterns were presented on more eccentric sites but did not as the low CCF patterns. However, sensitivity held constant as the magnified RF patterns were presented on more eccentric sites, indicating that the eccentricity effects observed for the high and moderate CCF patterns were neutralized by retinocortical mapping. Notably, sensitivity for the magnified RF patterns with large radii (4°–16°) presented in the peripheral field revealed a similar RF dependence observed for RF patterns with small radii (0.25°–1.0°) presented at the fovea in previous studies.

Eccentricity Effect in the Hole-Drilling Residual Stress Measurement

The paper focuses on the analysis of the eccentricity effect in the measurement of the hole-drilling residual stress. Relaxed strains were evaluated by computational simulation of the hole-drilling experiment using the finite element method. Errors induced by eccentricity were estimated for elastic and elastic-plastic states in area around the drilled hole due to the stress concentration. The invariance of the stress change with depth was assumed. The correction of eccentricity and plasticity effects in evaluation of residual stresses was realized within the EVAL 7 software (SINT Technology). The analysis shows that in elastic state the eccentricity and angular position of the drilled hole have a significant effect on relative residual stress errors. Correction according to the HDM method is very effective in this case. If the relative error of 5 % is allowed, which is in engineering practice acceptable, eccentricity of ±0.05 mm could be accepted without correction. When the combination of eccentricity and plasticity occurs, the correction of plasticity is more important in method 13-EXT-UN.