In recent years, permanent magnet (PM) vernier machines have gained more and more attention due to their high torque density and simple mechanical structure. However, PM vernier (PMV) machines with lap windings always suffer from long end winding length, and regular nonoverlapping winding may result in torque reduction for PMV machines. In this paper, an advanced PMV machine topology with multiple working harmonics is proposed. With specially designed stator auxiliary teeth, this topology could achieve ~20% higher torque density than that of a regular nonoverlapping winding PMV machine, with the same magnet usage. Through finite element algorithm and theoretical analysis, the production of additional flux density harmonics and their contributions to back-electromotive force (EMF) are verified. Moreover, the electromagnetic performances of this novel machine topology, such as back-EMF and output torque, are quantitatively investigated with the geometric parameters' effect considered. Finally, analysis results are verified by experimental test on a 21 Nm prototype, which is designed to have similar volume and weight with a 14 Nm regular commercial PM machine.

Analytical method for vibration and noise prediction in electrical machines is computationally efficient and widely used. In conventional analytical approaches, the slotted stator is simplified as a cylinder, and it is generally believed that the vibration is more sensitive to the air-gap forces with low spatial orders, hence, those high-order air-gap forces are usually neglected. In this paper, the force distribution on the slotted stator is analyzed using a force transformation model and a new phenomenon, i.e., the modulation effect, is found, which indicates that a high-order air-gap force could also induce a low-mode stator vibration with a large amplitude. As a result, the conventional analytical methods are not so accurate for machines with a strong modulation effect, such as fractional-slot concentrated-winding machines. The existence condition for the modulation effect is also discussed in this paper. Finite-element analysis and experiments have been done to verify the analysis results.

In recent years, permanent magnet vernier (PMV) machines are attracting more and more attentions owing to their high torque density. The spoke array magnet is widely used in the regular PM machine to improve working flux density. However, the flux barrier effect of spoke array magnet for the PMV machine has been proved, and a large torque reduction may be introduced in the spoke array PMV machine. In this paper, a novel spoke array PMV machine is proposed to improve working flux density and the torque density of PMV machines. The alternate magnetic bridges are added in the rotor core to connect iron pieces with same polarity and provide magnetic circuit for the low-pole number working magnetic field, hence the no-load back EMF and output torque of the proposed machine can be significantly improved. Moreover, analytical airgap flux density distribution based on equivalent magnetic circuit is presented to reveal the mechanism of working flux density improvement, and finite element analysis (FEA) is used to investigate the performance features and structure parameter influence on the key performances, viz. back EMF and torque, of the proposed machine. Finally, a 25Nm prototype has been built and tested to validate these analyses.

Fractional-slot concentrated-winding (FSCW) interior permanent magnet synchronous motors (IPMSMs) have been attracting considerable attention due to their high power density, high efficiency, short end winding, high slot fill factor, low cogging torque, excellent flux-weakening, and fault tolerance capability. However, compared to integral-slot distributed-winding (ISDW) IPMSMs, the key challenge of using FSCW configurations is the significant rotor losses, particularly at high speed. To figure out the IPMSM with which winding configuration is more suitable for electric vehicle (EV) application, the thermal behaviors of four IPMSMs with ISDW, single-, double-, and four-layer FSCWs are comprehensively and comparatively investigated in this paper. First, electromagnetic design and loss analysis of the four IPMSMs are investigated to meet the EV traction motor requirements. Second, finite-element method is employed to investigate the thermal performance of the IPMSMs under different rotational speeds and torque overload capacities. Thirdly, experiments implemented on an ISDW prototype are carried out to validate the presented analysis method. Finally, some conclusions are drawn for a suitable winding configuration selection and the PM traction motor design.

It is well known that permanent magnet Vernier machine (PMVM) has multiple flux field harmonics, which can produce stable torque. However, some flux field harmonics would create torque that undermines the total torque output. Such as the 6 slots 26 poles split-tooth PMVM here, of which modulated flux field outputs torque while fundamental flux field undermines torque output. In this article, a 26 pole PMVM with coding-shaped tooth is proposed. The coding-shaped tooth can introduce permeance harmonics with specific phase and amplitude, thus modulating flux fields that all output torque. Air-gap permeance harmonics of the proposed and the regular split-tooth PMVM are obtained via FEA. Based on MMF-permeance model, flux fields of two machines and their contributions to average torque are investigated, proving that the proposed machine has multiple flux fields that all output torque. Moreover, by optimizing geometric parameters of coding-shaped tooth, the proposed machine could obtain largest average torque and smallest torque ripple simultaneously. Electromagnetic performances of the optimized machines are studied comparatively in semianalytical way and FEA. It is proved that with same overall size, PM usage, and copper loss, the proposed machine could achieve 30% larger torque density, 86% smaller cogging torque, and 62% lower torque ripple than its counterpart. Finally, a 16-N·m (rated) prototype is built and tested.

This article presents an improved lumped parameter thermal network (LPTN) based online temperature prediction method of permanent magnet (PM) machines by global parameter identification. The proposed global parameter identification incorporates not only the loss but also the magnetic information into a fifth-order LPTN and identifies the multiphysical magneto-thermal parameters as a whole. In the identification process, the nonlinear characteristics, including the magnetic saturation, the cross-saturation, the strand skin effect, and the speed-dependent convective heat transfer, are all considered. It can eliminate the cumbersome magnetic and loss measurement efforts and improve the overall identification accuracy compared with the traditional step by step identification method. Based on the identified multiphysical magneto-thermal model, the critical temperatures of the PM machines, together with the online losses and torque, can then be predicted in real time. The experimental results show that the proposed online temperature prediction method can track the real temperature variation with errors within 5 °C.