Yuansheng An

The air gap magnetic field of the interior permanent magnet synchronous motor with the non-uniform air gap structure is affected by both local non-linear magnetic saturation and the non-uniform air gap, while the non-uniform air gap structure further affects the degree of magnetic saturation. However, the existing methods cannot consider the effect of the non-uniform air gap on magnetic saturation and cannot calculate the tangential air gap magnetic field. In this paper, a hybrid analytical model is proposed. Firstly the non-uniform air gap is converted to the uniform air gap through the air gap segmentation. The open-circuit air gap magnetic field with the equivalent uniform air gap is calculated by the hybrid analytical method. Then the permeance correction factor that can account for magnetic saturation is obtained, and the air gap magnetic field is calculated. Moreover, the influence of non-uniform air gap on tangential air gap magnetic field and the slotting effect are considered. Finally, the correctness of the proposed model is verified by a back electromotive force experiment and a magnetic field measurement. The proposed model has high accuracy and calculation efficiency and can provide a reference for the non-uniform air gap design.

In an interior permanent magnet synchronous motor (IPMSM) with segmented skewed poles, the armature reaction magnetic field (AR-MF) changes nonlinearly due to the saturation of the rotor magnetic barrier. Meanwhile, this varies under different excitation currents. As a result, it is difficult to be calculated by means of analytical methods. In this paper, the calculation model of AR-MF of IPMSM is first established by vector superposition method, without considering the saturation effect of rotor and the slotting effect of stator. In the second step, the virtual magnetic field of the rotor is introduced to quantitatively calculate the influence of local inhomogeneous saturation on the AR-MF. The latter is derived by combining both the subdomain method and equivalent magnetic circuit method. The complex relative permeance is also introduced to establish the AR-MF accounting for the stator slotting effect. To validate the AR-MF calculation method proposed, an 8-pole 48-slot IPMSM with segmented skewed poles is considered as a case study, showing a comparison by both with finite element (FE) results and the electromagnetic torque measured on a test bench. The model proposed in this paper shows high accuracy and fast computation with respect to FE analysis.

Due to the local inhomogeneous magnetic saturation of the core of the interior permanent magnet synchronous motor (IPMSM), the magnetic field changes nonlinearly, which makes the analytical calculation of the magnetic field difficult. Therefore, the calculation of the magnetic field mostly relies on the finite element method (FEM). However, the high computation cost of FEM restricts the efficiency of the design and analysis of IPMSM. In this article, an analytical model (AM) of slotless open-circuit air-gap magnetic field (OC-AG-MF) of IPMSM with V-shaped segmented skewed poles is derived by combining the subdomain method (SDM) and the magnetic equivalent circuit (MEC) method, and then, the AM of slotted OC-AG-MF of IPMSM with V-shaped segmented skewed poles is obtained by introducing the complex relative permeance. To show the effectiveness of the novel AM, the OC-AG-MF and cogging torque of an IPMSM with V-shaped segmented skewed poles for electric vehicles are calculated by the AM and FEM, respectively. The spatial order, amplitude–frequency characteristics, and the 3-D spatial distribution of the OC-AG-MF are analyzed. Finally, the accuracy of the AM is experimentally verified by direct measurement of OC-AG-MF and no-load back electromotive force (EMF) of the motor. The AM proposed in this article is shown to accurately calculate the radial and tangential components of OC-AG-MF of IPMSM with V-shaped segmented skewed poles considering rotor magnetic bridge saturation effect and stator slotting effect. Meanwhile, the efficiency of the design and analysis of the motor is expected to be improved due to the reduced computational effort compared to the prevalent FEM.

3-D analytical model and direct measurement method (DMM) of ultra-thin open-circuit air-gap field (OCAGF) of interior permanent magnet synchronous motor (IPMSM) with multi-segmented skew poles (MSP) and multi-layered flat wire windings (MFWW) for electric vehicles (EV) are proposed. Basis functions of slotless OCAGF are derived through field reconstruction method (FRM). In order to consider MSP and slotting effects, a complex relative permeance function is extended from 2-D to 3-D. Based on the magnetic potential and permeance method, 3-D analytical model of OCAGF is obtained. Then the back electromotive force (BEF) is calculated through Faraday's Law and the cogging torque is obtained through Maxwell stress tensor method. Furthermore, spatial order and amplitude-frequency characteristics of OCAGF are revealed. Additionally, influence of local inhomogeneous saturation caused by PM materials on analytical accuracy is discussed. Finally, the proposed analytical model is verified through both the traditional indirect measurement methods (BEF measurement and cogging torque measurement) and a novel direct measurement method, in which ultra-thin OCAGF of 10-1 mm order of magnitude can be measured directly. Local microscopic characteristics of OCAGF in some important locations, such as tooth top and magnetic bridge, can be accurately detected by using of the direct measurement method.