Influence of manufacturing tolerances and eccentricities on the unbalanced magnetic pull in permanent magnet synchronous motors

Abstract This study presents the dependence of the level and harmonic structure of the cogging torque in permanent magnet synchronous motors (PMSM) to imperfections of permanent magnet (PM) dimensions and positions, which can not be avoided in massproduction. Slightly diverse dimensions and misplacements of PMs are introducing asymmetries in magnetic field distribution which cause additional harmonic components. A finite element method (FEM) and Fast Fourier transform (FFT) were used to calculate cogging torque harmonic components with regard to several combinations of PM assembly imperfections. It has been established and proved that unequal PMs cause magnetic asymmetries which give rise to additional cogging torque harmonic components and consequently increase the total cogging torque. It is also shown that in some particular combinations the influence of an individual PM imprecision could compensate with others due to different phase shifts which can result even in the decrease of cogging torque. Considering presented results it is possible to foresee which additional harmonic components will comprise the cogging torque of mass-produced PMSMs due to PM imperfections. In this way the designers are able to predetermine required manufacturing tolerances to keep the level of cogging torque in a admissible level. Simulation results were verified and confirmed by laboratory tests.

Download Full-text

Analysis of Nonlinear Vibration in Permanent Magnet Synchronous Motors under Unbalanced Magnetic Pull

Applied Sciences ◽

10.3390/app8010113 ◽

2018 ◽

Vol 8 (1) ◽

pp. 113 ◽

Cited By ~ 4

Author(s):

◽

Yan Bai ◽

Bo Yang ◽

He Li

Keyword(s):

Permanent Magnet ◽

Nonlinear Vibration ◽

Permanent Magnet Synchronous Motors ◽

Synchronous Motors ◽

Unbalanced Magnetic Pull

Download Full-text

Influence of unbalanced magnetic force on shaft deflection in permanent magnet synchronous motor with fractional slot concentrated windings

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-209466 ◽

2020 ◽

Vol 64 (1-4) ◽

pp. 1461-1468

Author(s):

Ting Dong ◽

Juyan Huang ◽

Bing Peng ◽

Ling Jian

Keyword(s):

Permanent Magnet ◽

Magnetic Force ◽

Permanent Magnet Synchronous Motor ◽

Operational Reliability ◽

Topology Structure ◽

Permanent Magnet Synchronous Motors ◽

Synchronous Motors ◽

Shaft Deflection ◽

Large Length ◽

Fractional Slot

The calculation accuracy of unbalanced magnetic forces (UMF) is very important to the design of rotor length, because it will effect the shaft deflection. But in some permanent magnet synchronous motors (PMSMs) with fractional slot concentrated windings (FSCW), the UMF caused by asymmetrical stator topology structure is not considered in the existing deflection calculation, which is very fatal for the operational reliability, especially for the PMSMs with the large length-diameter ratio, such as submersible PMSMs. Therefore, the part of UMF in the asymmetrical stator topology structure PMSMs caused by the choice of pole-slot combinations is analysized in this paper, and a more accurate rotor deflection calculation method is also proposed.

Download Full-text