Search

The forward computational modal analysis (CMA) of the motor stator assembly is gaining attention as a technical challenge in the area of motor noise. There is still no effective method to obtain accurate anisotropic material parameters (AMPs) required for CMA without prototype motors. In this paper, a novel forward calculation method (FCM) for calculating AMPs of the motor stator assembly is proposed, in considering structural discontinuities and composite material properties due to core lamination and winding stacking. The method is based on multi-scale theory. Firstly, the multi-scale equations coupling the macroscopic model and the mesoscopic model of the stator core and winding are established. By decoupling the multi-scale equations, the equivalence and equivalence preconditions of AMPs of the two scale models are described. Accordingly, the finite element method (FEM) for calculating AMPs of the stator core and winding based on the mesoscopic model is proposed. Then, the AMPs of the stator core and winding are calculated by the FCM, and the influencing factors are further studied, respectively. Finally, the effectiveness of this method is verified by modal experiments. Compared with experimental results, the maximum relative error of natural frequencies of the stator assembly is within 1.5%. This method can achieve accurate CMA without prototype motors and modal experiments, which contributes to the accurate prediction and control of electromagnetic noise in the initial motor design stage. [ABSTRACT FROM AUTHOR]

In this study, the air gap magnetic field characteristics of external rotor permanent magnet synchronous motors (PMSMs) under both the stator and rotor coordinate systems considering low‐order current harmonics and high‐order sideband current harmonics are analysed. A direct measurement technique (DMT) for air‐gap magnetic field is proposed. First, an analytical model of air gap magnetic field of external rotor PMSMs is established. The spatial order and frequency characteristics of stator/rotor air gap magnetic field are revealed. Then, a 24‐pole 27‐slot external rotor PMSM is taken as an example. The analytical and finite element (FE) results are compared and analysed. The difference of the spatial order and frequency characteristics between the stator and rotor air gap magnetic field are verified. Next, a new DMT is proposed, which can detect the precise distribution and local microscopic characteristics on the order of 10−1 mm with high resolution. The accuracy of analytical and FE model are verified by the DMT and an indirect experimental test of no‐load back electromotive force. Finally, the mechanical challenges of in‐wheel motors and the practicablility of DMT for eccentricity detection are further discussed. [ABSTRACT FROM AUTHOR]

The no‐load radial magnetic field and no‐load back electromotive force (EMF) of external rotor permanent magnet brushless DC motor (PMBLDCM) are calculated by applying the correction coefficient of magnetic conductance here, taking into account the stator slotting and static eccentricity effects. An external rotor PMBLDCM with 51‐slot/46‐pole, used as in‐wheel motor, is taken as an example, the analytical calculation results of the no‐load back EMF are validated by the finite‐element method and experiment. The influences of static eccentricity ratio on the no‐load radial magnetic field and no‐load back EMF are investigated based on the analytical model. The investigation shows that static eccentricity does not change the harmonic contents of no‐load radial magnetic field, so it does not change the harmonic contents of three‐phase no‐load back EMFs. However, static eccentricity changes the space order of no‐load radial magnetic field, resulting in the different total harmonic distortions of three‐phase no‐load back EMFs; in other words, the asymmetric distortions of three‐phase no‐load back EMFs are generated. The asymmetric distortions of three‐phase no‐load back EMFs are intensified with the increase in static eccentricity ratio. [ABSTRACT FROM AUTHOR]

Here, analytical expressions of the unbalanced magnetic force (UMF）of the stator and the rotor under static eccentricity (SE) are deduced by using complex relative magnetic conductivity method and Maxwell stress tensor method. The frequency characteristics of the UMF are obtained. Further the influence of different eccentricity ratio on the UMF is researched. Then, an external rotor permanent magnet brushless direct current motor (PMBLDCM) with 46 poles and 51 slots used as an in‐wheel motor is taken as an example to verify the frequency characteristics by finite element analysis (FEA). The research shows that the frequency characteristics of the UMF of the stator s related to electric frequency. The frequency characteristics of the UMF of the rotor are related to the power source frequency and the rotation frequency of the wheel. It does not introduce new frequency components when the motor SE occurs. As the SE ratio increases, the amplitude of the UMF increases. The UMF without eccentricity exists in all directions with the change of the time. However, as the eccentricity ratio increases, the direction of the UMF is closer to the eccentric direction. [ABSTRACT FROM AUTHOR]

This study presents an analytical model for calculating the armature reaction magnetic field of outer rotor permanent magnet brushless DC motor (PMBLDCM) in stator stationary coordinate system (SSCS) and rotor rotation coordinate system (RRCS). Firstly, an expression of armature reaction magnetic field of single‐phase winding is deduced, without considering slotting effect. Afterwards, analytical expressions of armature reaction magnetic field in both SSCS and RRCS regardless of slotting effect are obtained using vector addition method. Then complex relative permeances of outer rotor BLPMDCM in SSCS and RRCS are analysed, respectively. Finally, analytical solutions of the armature reaction magnetic field in both SSCS and RRCS are derived, respectively, by multiplying the slotless armature reaction magnetic field and the complex relative magnetic permeance, the self‐ and mutual inductance are calculated by the armature reaction magnetic field. A 46‐ploes‐51‐slots outer rotor BLPMDCM is set as an example, the accuracy of proposed analytical model is verified by the Finite Element Method. Based on this analytical model, the pattern of slotting effect on armature reaction of both outer rotor and internal stator are analysed, respectively, as well as spatial order characteristics and frequency characteristics of armature reaction for outer rotor PMBLDCM in SSCS and in RRCS. [ABSTRACT FROM AUTHOR]

An analytical method for calculating the no-load magnetic field of external rotor permanent magnet brushless direct current motor (PMBLDCM) used as in-wheel motor of electric vehicle in the stator static coordinate and the rotor motion coordinate is presented in this paper. First, the analytic formulas of slotless permanent magnetic field in both coordinate systems are derived, respectively. Then, the complex relative permeance of external rotor PMBLDCM in both coordinate systems is calculated. Finally, the analytical solution of the no-load magnetic field in both coordinate systems is derived by applying the magnetic potential multiplied by the complex relative permeance. In this paper, a 46-pole-51-slot external rotor PMBLDCM is taken as an example, and the accuracy of the proposed analytical model is verified by the finite-element results. Based on the analytical model, the influences of the stator slotting effect on the no-load magnetic field of the external rotor and the inner stator are analyzed. The spatial order characteristics and frequency characteristics of the no-load magnetic field of the external rotor PMBLDCM in both coordinate systems are revealed, respectively. [ABSTRACT FROM AUTHOR]