This paper presents an analytical model for the prediction of the performance in a spoke-type permanent magnet synchronous in-wheel motor with trapezoid magnet accounting for tooth saturation. The impact of magnet shape on modeling is considered. To match the standard boundary conditions, the trapezoid magnet is simplified to sector magnets. According to the invariance principle of the magnetic field created by magnet, the dimension of the sector magnet is calculated with lumped magnetic circuit model. Then the motor is divided into six subdomains, i.e., shaft, inner sector magnet, outer sector magnet, rotor slot, air-gap, and stator slot. Based on the boundary conditions, the magnetic field, back-EMF, and torque are obtained by solving the Poisson's and Laplace's equations. The effect of tooth saturation is considered. The finite element method and experiments are employed to validate the accuracy of the analytical model. In addition, the proposed method can also be used to evaluate the performance of the spoke-type motor with any irregular magnet.

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 paper presents an accurate modeling method to investigate the thermal performance of the windings under steady state. The model considers the heat conduction of active windings and heat convection of end windings. To verify the validity of this model, a 20/24 poles/slots permanent magnet (PM) in-wheel motor is taken as an example. Firstly, the temperature distribution of the active windings in the slot is calculated by a multi-block 2-D temperature field model, which is verified by the model built according to the reality. The numerical results of blocks model agree well with those of the real model. Secondly, a 3-D temperature field model with the end windings is built on the 2-D blocks model. Furthermore, to include the air inside the motor, computational fluid dynamics (CFD) has been utilized, and the numerical results are experimentally verified. Finally, the distribution of the heat transfer coefficient (HTC) of the end windings and the influence of rotor speed on the HTC are investigated. These HTCs acquired from CFD results and empirical formulas are compared and analyzed carefully.

This article investigates the asymmetric temperature distribution of a modular permanent magnet (PM) synchronous in-wheel motor under fault conditions, and based on this, proposes a fault-tolerant (FT) strategy named minimum temperature difference strategy (MTDS) to avoid the high temperature appearing at local winding. First, the modular motor system and the FT principle are introduced, and the reconfiguring fundamental magneto motive force (MMF) under open-circuit of one phase in one module is deduced. Second, the loss and temperature distributions of the motor with normal operation are analyzed by the coupled electromagnetic–thermal method. And the mutual verification between simulation and experiment is adopted to separate the copper losses, iron losses, and PM losses from total losses. Furthermore, the asymmetric temperature distributions of the motor operating with part of modules are analyzed in detail. Finally, the influence of the faulty windings on the temperature of healthy windings is investigated, and the FT strategy of MTDS is proposed. The asymmetric temperature distributions of the motor under various FT strategies are compared. The result shows that the MTDS can significantly reduce the maximum temperature of the windings and makes the winding temperature distribution more uniform.

In this article, the thermal properties of axial flux permanent magnet motors are investigated. A modified cooling structure is designed to enhance the cooling performance for end windings compared with the conventional cooling structure. The heat flow path in the end thermal conduction region is studied based on the lumped-parameter thermal network model. The influence of the thermal conductivity of potting material and the thickness of stator yoke on cooling performance is discussed. The computational fluid dynamics thermal analysis is also employed to give verification and to get the temperature of hot spot. In the end, a prototype motor with the modified cooling structure is tested.

The amorphous alloy material has the characteristics of high resistivity and low loss, but the loss characteristic of the amorphous alloy core is unstable, which can be greatly affected by the processing. Thus, the calculation error of the amorphous alloy core loss turns out to be large, which leads to the difficulty in the design and optimization of the core. In this paper, a new loss factor correction model of amorphous alloy core is proposed to analyze the influence of the processing and core size on the loss. In order to verify the loss factor correction model, the loss characteristic of amorphous alloy material was tested and analyzed, and the core loss at different core sizes was compared. In addition, a mathematical model of core loss is proposed for the amorphous alloy stator core to optimize and calculate the loss of amorphous stator core. The correctness of the proposed model is verified by the test of core loss.