Nowadays, in-wheel drive mode is considered as one of the most promising modes for electric vehicles (EVs). The motor type plays a significant role in the vehicle performances. This article focuses on the performance between permanent magnet synchronous motor (PMSM) and permanent magnet Vernier motor (PMVM) for in-wheel direct drive. First, the required performances are determined by the vehicle requirements. The prototypes of PMVM and PMSM are manufactured after the comparison. Then, the expressions of air-gap magnetic field harmonic, electromagnetic torque, and power factor are theoretically derived, where the parameter torque ratio is introduced to evaluate the torque ratio between PMVM and PMSM. Based on experiment, the back-electromotive force harmonics, cogging torque, maximum torque per ampere capability, flux-weakening capability, torque, efficiency, and power factor are compared and analyzed. Subsequently, the discussions are carried out, where the strength and weakness of two-type motors for in-wheel drive are concluded and the future prospects are suggested. Finally, the conclusions of two-type in-wheel motors are then extracted. This article aims at providing a reference for the exploration of alternating in-wheel motor types, which can promote the development of high-performance in-wheel drive system for EVs.

This paper mainly studies the influences of air-gap deformations on the electromagnetic performances and radial vibration characteristics of an interior permanent magnet synchronous motor (IPMSM) at peak rotating speed with rated power. Considering different air-gap states in the electromagnetic finite element models of investigated IPMSMs, the effects of stator oval deformation, rotor centrifugal distortion, and both deformations on the air-gap magnetic flux field, radial and tangential magnetic force and electromagnetic torque are analyzed and compared, respectively. Then, based on the accurate structural model of the stator system, the motor vibration characteristics are investigated with loading different electromagnetic force excitations on the stator inner face. Finally, the vibration experiments of the investigated IPMSM prototype are carried out to verify the results obtained by the simulations at high-speed load condition. It is found that the air-gap deformations give a large increase in the particular vibration level. In order to improve the prediction accuracy of motor vibration characteristics, the air-gap deformations under all electromagnetic excitations, including magnetic force and torque pulsation, should be taken into consideration.

Permanent magnet vernier (PMV) machines, as one of the flux modulation machines, are getting increasingly attention due to inherent high torque density and low torque ripple. This paper mainly investigates the torque performance of PMV machines with different stator tooth topologies. Firstly, it begins with the theoretical analysis of surface-mounted PMV machines, which has a generic number of flux modulation poles (FMPs), PM poles and armature poles. Then, the expression of flux linkage, back-EMF and electromagnetic torque are derived successively, where the equivalent winding factor is proposed and defined to evaluate the flux modulation of stator auxiliary teeth and multi-harmonics coupling effect. Next, the back-EMF, torque, power factor, flux weakening capability and PM demagnetization of PMV machines with different number of stator teeth are analyzed and compared. The final results of theoretical analysis and finite element analysis (FEA) can match well. Meanwhile, the non-uniform distribution of FMPs for increasing the average torque is firstly proposed and analyzed. A parameter K titled as flux modulation pole ratio is defined to evaluate the relationship among the angles among FMPs, the influence of the variation of K on the back-EMF and torque is deeply explored and analyzed. Besides, the optimal range of K is carefully validated, which will help to optimize the design parameters more conveniently in the future.

This study investigates the accurate modelling and the modal natural frequencies of the stator system of a permanent magnet synchronous motor with concentrated winding used in the in‐wheel motor system of the electric vehicle. The equivalent material physical properties of each component in the stator system are determined by the correction formula and the empirical coefficient. Meanwhile, the contact conditions between each component are also analysed. According to the structural analysis of stator system, different equivalent finite‐element models of winding and frame, together with their effects on the accuracy of simulation results, have been built and investigated, respectively. In addition, the prototype of the motor is fabricated; then the experimental modal analysis of the stator system and its subassemblies are carried out during the manufacturing process. Through comparisons of the results between experiments and finite element anaysis (FEA), the final model of the stator system is determined and verified to be of high accuracy to predict the vibration behaviours of the investigated motor with concentrated winding. Finally, several factors influencing the modal frequencies of stator system are analysed, which could provide certain reference value to the structural design of stator system.

Interior permanent magnet (IPM) motors are widely used in electric vehicles (EVs), benefiting from the excellent advantages of a more rational use of energy. For further improvement of energy utilization, this paper presents an analytical method of d- and q-axis inductance calculation for IPM motors with V-shaped rotor in no-load condition. A lumped parameter magnetic circuit model (LPMCM) is adopted to investigate the saturation and nonlinearity of the bridge. Taking into account the influence of magnetic field distribution on inductance, the winding function theory (WFT) is employed to accurately calculate the armature reaction airgap magnetic field and d- and q-axis inductances. The validity of the analytical technique is verified by the finite element method (FEM).