In this paper, the end forces caused by the longitude end effects in linear permanent magnet synchronous machines (LPMSMs) are analyzed and minimized. First, the left/right-end forces are calculated based on an analytical model and the Maxwell stress tensor, in which the optimal integration surfaces are investigated. Then, based on the spectrum analysis of the left/right-end forces, two different methods are adopted to minimize the fundamental and high-order harmonics, respectively. The optimal length of the primary iron is obtained from the phase difference of the fundamental and a two-step iteration instead of the trial-and-error with the finite element method. Furthermore, step-skewed auxiliary irons are added to the primary end to eliminate the high-order harmonics. Third, to reduce the secondary end effect when the primary moves to the secondary end, a compensation method of adding mirror permanent magnet is proposed and good results are obtained. Finally, an LPMSM prototype is manufactured and experiments are conducted. The experimental results verify the theoretical study.

As a wheel traction motor used for electric vehicles (EVs), due to the requirement of high power/torque density and the poor working condition, it is more prone to cause severe inter- turn short circuit (ITSC) faults. In this paper, the ITSC faults characteristics of a permanent magnet synchronous machine (PMSM) used for wheel traction motors in EVs are deeply and comprehensively researched. The influence of fault intensity on machine's parameters and performance are researched at different fault resistances through finite element method (FEM). Besides, factors that affect the amplitude of short circuit current are researched by mathematic formula and simulation, including load state, rotation speed, fault position and branch inductance. Then, the loss and thermal characteristics of the PMSM under different conditions are analyzed. In the last, experiments are conducted to validate the simulation results.

This paper presents an improved analytical method for predicting the magnetic field and forces in linear permanent-magnet synchronous machines (LPMSMs) accounting for both the primary end effect and secondary end effect. So far, the magnetic field calculation of LPMSM in most studies is conducted in Cartesian coordinate, whereas the end effect is neglected by applying periodic boundary. In this paper, to implement the analytical model, a polar presentation of the machine geometry is proposed and the subdomain method is applied to calculate the magnetic field. Then, according to the developed model, the tangential thrust and normal forces are calculated based on the Maxwell stress theory. Numerical results are subsequently obtained by finite-element method and employed to validate the analytical model. Finally, an LPMSM prototype is manufactured and experiments are conducted. The results show that the developed analytical model has high accuracy for predicting the magnetic field and forces.

In this paper, an improved magnetic equivalent circuit (MEC) model of a coreless axial-flux permanent-magnet synchronous machine (AFPMSM) with printed circuit board (PCB) winding is presented, which considers the curvature effect, fringing effect, leakage flux, and rotor yoke's magnetic saturation. The axial air-gap flux density distribution, no-load back electromotive force, winding inductances, and electromagnetic torque are predicted by the proposed MEC model. The steady-state performances of the machine under heavy load, as well as the dynamic response of the machine with a connected voltage source and mechanical load, are calculated. All the results obtained from the proposed model are in good agreement with those issued from the 3D finite element method (FEM). The computation time of the proposed model is greatly reduced compared to 3D FEM. Finally, a coreless AFPMSM prototype with a PCB stator is manufactured, and experiments are carried out to verify the predicted results.

The cogging force is a main component of the detent force in the permanent magnet linear synchronous motor (PMLSM). It will lead to the thrust ripple and deteriorate the control characteristics, which cannot be neglected especially in precision machine tools. In order to minimize the cogging force, a novel double-sided PMLSM structure with reversed slots is proposed and compared with a conventional PMLSM in this paper. Two novel windings are further added to compensate the unbalanced back electromotive force (EMF) caused by the reversed slots. With this suggested structure, an 8-pole 9-slot double-sided PMLSM is designed. And its detent force and back EMF are evaluated with the help of the 2-D finite element analysis. Finally, a prototype of the double-sided PMLSM with reversed slots is developed, and experiments are carried out to verify the analytical and simulated results.

A comparative study of five-phase outer-rotor flux-switching permanent magnet (FSPM) machines with different topologies for in-wheel traction applications is presented in this paper. Those topologies include a double-layer winding, a singlelayer winding, a C-core, and an E-core configurations. The electromagnetic performance in the low-speed region, the fluxweakening capability in the high-speed region, and the faulttolerance capability are all investigated in detail. The results indicate that the E-core FSPM machine has performance advantages. Furthermore, two kinds of E-core FSPM machines with different stator and rotor pole combinations are optimized, respectively. In order to reduce the computational burden during the large-scale optimization process, a mathematical technique is developed based on the concept of computationally efficient finite-element analysis (CE-FEA). While a differential evolution (DE) algorithm serves as a global search engine to target optimized designs. Subsequently, multi-objective tradeoffs are presented based on a Pareto-set for 20,000 candidate designs. Finally, an optimal design is prototyped, and some experimental results are given to confirm the validity of the simulation results in this paper.