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In this article, a novel magnetic field calculation approach that considers the static inclined eccentricity of axial flux permanent magnet (AFPM) machine is presented. The equivalent remanence of permanent magnet (PM) is introduced and calculated, in which the air-gap length can be regarded as uniform. Then, the analytical model based on harmonic subdomain technology can be used directly. The magnetic field distribution (MFD) and electromagnetic performance under eccentric state are calculated and compared. The effectiveness of the proposed method is verified both by the finite element (FE) model and experimental results. The main contribution of this article is to provide a simple and accurate method for the calculation of the eccentric magnetic field of the PM motor, not limited to the AFPM. [ABSTRACT FROM AUTHOR]

The tubular linear oscillating machine can achieve reciprocating movement directly without auxiliary transmission mechanisms, which is widely used in the free-piston energy conversion system. To achieve a lower thrust ripple and eliminate the eddy current effect, a circumferential silicon steel stack is usually utilized in the stator, however, it results in assembling difficulties. In this article, a radially split lamination tubular linear permanent magnet oscillating machine with auxiliary configuration (RSL-TLPMOMA) is proposed to solve the problem. First, the laminated coefficient expression of split-laminated is deduced, the influence of laminated number and radius ratio on laminated coefficient is discussed, and the optimal combination of the laminated number under different radius ratios is given. Second, the subdomain (SD) method is used to analyze RSL-TLPMOMA, the auxiliary teeth, slot, and end effect are considered. Finally, a prototype is manufactured and tested. [ABSTRACT FROM AUTHOR]

To facilitate the active magnetic bearing (AMB) design and analysis, an accurate and fast model that considers both rotor eccentricity and the saturation effect is necessary. In this article, a novel hybrid analytical model (HAM) for effective calculation of the magnetic field of the AMB is proposed. Eccentricity and local saturation are considered in the proposed HAM. In the proposed HAM, the stator and rotor are modeled by elementary subdomains (ESDs) and the air-gap is modeled by magnetic equivalent circuit (MEC). Direct coupling between the solutions in the ESD regions with MEC completes the whole model matrices. Compared to the existing literature, the proposed model considers both the rotor eccentricity and material nonlinearity. The effectiveness and accuracy of the proposed HAM are validated by both the finite element model and experimental results. The results show that the proposed HAM can accurately predict the magnetic quantities of the AMB. [ABSTRACT FROM AUTHOR]

This article proposes a rotor design method suitable for double-layer interior permanent magnet synchronous motor (DIPMSM), which can reduce electromagnetic torque ripple and at the same time reduce the electromagnetic noise of the motor. In previous studies, the inverse cosine function (ICF) was used to modify the rotor shape for making the air-gap flux density distribution sinusoidal under no-load conditions, which can reduce the torque ripple. However, conventional ICF can only be used in a single-layer interior rotor structure. Consequently, this article proposes a piecewise inverse cosine function (PICF) based on ICF, which can be applied to DIPMSM. To verify the improvement of the proposed method in the electromagnetic and noise aspects of the motor, the electromagnetic model and a noise prediction model of the 36-slot/8-pole motor are established by the finite element method. The PICF model is compared with the prototype in the aspects of electromagnetic performance and noise. The torque ripple is reduced by 54.16%, from ±2.4 to ±1.1 N m, and the electromagnetic noise is reduced by about 4.9 dB. Finally, the accuracy of the noise prediction model is verified by the noise test of the prototype. [ABSTRACT FROM AUTHOR]

In this paper, a new hybrid model is proposed for the prediction of air gap magnetic field distribution (MFD) in interior permanent magnet machines with any rotor configuration. The slotless magnetic field is first predicted by finite-element method (FEM) with automatic scripting in MATLAB to consider saturation in the rotor iron. Afterward, the conformal mapping viz., Schwarz–Christoffel mapping is introduced to take the slotting effect into account. Consequently, the MFD could be calculated. The back electromagnetic forces, cogging torque, and output torque are obtained accordingly. Then a subdomain model is developed to consider the armature reaction. The results show that the proposed hybrid approach agrees well with the FEM. The model is further verified by experiments. The main contribution of this paper is to reduce the computation time remarkably while maintaining the calculation accuracy. [ABSTRACT FROM AUTHOR]

In this paper, a general analytical model is proposed to calculate the back electromotive forces of various manufacturing imperfections in the double-rotor axial flux permanent magnet machine. First, the axial and circumferential flux density in the air gap under healthy condition is developed by Maxwell’s equations and Schwarz–Christoffel mapping. Second, the equations of air gap length and radii are introduced to calculate the flux density with manufacturing imperfections. The back EMFs of each case are calculated. For each case, finite-element (FE) method models are developed to validate the analytical model, and the results show that the analytical model predictions match well with the FE results. Finally, the analytical model is verified by experimental results. [ABSTRACT FROM AUTHOR]