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The main limitation of magnetic gears is their relatively low torque density. Therefore, a novel structured high torque density magnetic-geared permanent magnet (MGPM) machine, which combines the advantages of a conventional MGPM machine and magnetic gear to enhance the torque considerably and achieve low-speed high-torque operation, is proposed in this study. However, there are different structures for increasing torque of a machine. Therefore, in order to demonstrate the advantages of the proposed structure, it is compared with other structures, using the finite element method. Moreover, the proposed MGPM machine can transmit an additional 42.3% of torque density when compared with the conventional MGPM machine of the same size.

Recently, a motor for an in-wheel system—which is advantageous when applied to electric vehicles and self-driving systems—has received much attention. In this paper, we propose an analysis and design method that can be used for an in-wheel motor. In-wheel motors require high torque density and a compact form factor to be wheel-mounted. To meet these requirements, an axial flux permanent magnet motor is proposed for the in-wheel system. The end-winding length of the coil is a key factor to be considered in this design. Hence, we propose a novel method to study the end-winding length. Due to the structural characteristics of an axial flux permanent magnet motor, a three-dimensional finite element analysis, which requires much time and expense, is essential. To solve this problem, we propose a novel analytical method combined with finite element analysis to mitigate the time and cost factors in the development of the axial flux permanent magnet motor. The magnetic saturation and the slot opening effect, which are considered during the analysis and design phase, are extremely difficult to analyze due to their nonlinearity. Therefore, a novel analytical method and algorithm, which can consider nonlinear effects, such as the magnetic saturation and slot opening, is proposed. The usefulness of the proposed analysis and design method and the axial flux permanent magnet motor for an in-wheel system were verified via 3D finite element analysis using a commercial simulation tool (JMAG).

A high gear ratio flux switching permanent magnet machine (HFSPM) was proposed to improve the torque performance in flux switching permanent magnet machine (FSPM). Conventional FSPMs address flux bypass issue when designed with a high gear ratio. The HFSPM adopts a dual rotor structure to overcome this flux bypass issue. First, the cause and effect of flux bypass issue was discussed using a magnetic equivalent circuit (MEC). Further, the process of overcoming the flux bypass issue using dual rotor structure was discussed. An alternative HFSPM, consequent pole HFSPM (CP-HFSPM), was proposed to enhance torque performance. The CP-HFSPM was optimized for high torque performance and proper power factor.

High-torque-density electrical machines applied to traction operate at a varying torque and speed, and therefore, when minimizing the torque ripple, a wide variety of possible loads must be considered. Different loads need different current vectors, which affect the magnetic state of the machine. Thus, the torque ripple must be analyzed by using appropriate current vectors as it is proposed and described in this paper. The torque ripple values were estimated also for a skewed machine using a new method of torque ripple estimation of a skewed machine. The method is computationally less heavy and allows computing the torque ripple at all possible load points. Using the proposed method in the analysis of the machine parameters, the rotor pole geometry was adjusted to minimize the torque ripple without degradation of the other properties of the machine. Finally, the best machine performance was compared with the measured results.

Permanent magnet motor is an attractive candidate for its utilization in electric vehicle. In this paper, an interior V type permanent magnet (IVPM) motor with strengthening rib and magnetic bridge is proposed for the electric vehicle. Firstly, the windings arrangement of IVPM motor is adopted by double layer fractional-slot distributed winding (FSDW), which purpose is to improve the filed weakening capability and heat emission performance of IVPM. Secondly, some simulation analysis of IVPM motor based on the different width of strengthening rib and magnetic bridge are completed. Lastly, an IVPM motor prototype is constructed and tested. The comparison results between simulation analysis and test show that the proposed IVPM motor has the advantage of high torque density and high efficiency in the constant torque region (1000rpm ~4000rpm). Besides, in the rate and peak running condition of IVPM, the results of prototype simulation and test indicate that the proposed IVPM motor has a reasonable temperature rise.

This paper presents a new method to calculate the cogging torque of the permanent magnet synchronous machine under load condition. Combined with the mathematical expression of the cogging torque, it is found that the cogging torque will be influenced by the load. In order to accurately analyze the torque ripple of the motor at low speed and high torque operation and make it possible to reduce the cogging torque under load condition, it is necessary to calculate the cogging torque accurately. A calculation method for the on-load cogging torque of the PMSM, which the cross magnetization and core saturation have been taken into consideration, is proposed in this paper. The finite element analysis (FEA) and field-oriented control (FOC) contribute to the method, which mainly consists of three parts: elimination of the reluctance torque, calculation of the average torque, and the ripple torque and the separation of the cogging torque. By using this method, the cogging torques of a 16-pole/24-slot PMSM under different load conditions has been calculated. The result shows a very good agreement between simulation and experiment, which verifies the feasibility and effectiveness of the proposed method.