The coreless axial flux permanent magnet synchronous motor with printed circuit board stator (PCB motor for short) has attracted research interests for many advantages, such as flexible and precise winding design, low toque ripple, noiseless operation and simple manufacturing process. The motor performance, however, highly depends on its wiring design, which should be carefully optimized. In this article, an arc-shaped distributed winding is adopted due to its higher efficiency. The PCB motor has a 3D magnetic field distribution, which makes its optimal design very difficult since the 3D finite element analysis is usually required. In this article, an analytical model of PCB motor including 3D magnetic field, arc-shaped winding flux linkage and eddy current loss is firstly deduced. On this basis, a multi-objective optimal design is then carried out to design a PCB motor for a vacuum cleaner. Compared with the concentrated winding, the arc winding can achieve a 3% efficiency improvement. Finally, a 130 W prototype and testbench were built and the presented analytical model is verified by experiments. The results show that there is little difference between calculation and experiment. The presented method effectively simplifies the design process of this kind of motor and shortens the design time.

A hysteresis motor produces output torque through the hysteresis effect of magnetic materials. It has the advantages of a simple structure, high-speed operation, high temperature resistance, low noise and self-starting capability. It can be applied to some special occasions requiring high speed and high stationarity. However, its disadvantage is low torque density, low efficiency and low power factor. The permanent magnet hysteresis motor is a compromise of the characteristics of permanent magnet motor and hysteresis motor, and it can be self-starting in the case of having a torque density comparable to that of a permanent magnet motor. In addition, there are some new structures of hysteresis motors, which open up the direction for innovative applications. Due to the complexity of magnetic properties, the calculation methods and dynamic models of hysteresis motors and permanent magnet hysteresis motors are special and also depend on the research of hysteresis materials and hysteresis models. This paper starts from the principle and classification of the hysteresis motor, and different structures and the corresponding analysis methods are reviewed. The motors with new structures and new methods are emphasized, the innovation and contribution of existing research are summarized, and the development trend of hysteresis motors is described.

This article presents an effort to develop an effective method for the robust design optimization of a hairpin winding permanent magnet motor. The comprehensive influence of variable uncertainties due to PM property inconsistency and manufacturing uncertainties is considered. During the implementation of robust design optimization of the hairpin winding permanent magnet motor by using an evolution-based multi-objective optimization algorithm, one major obstacle is the huge computation cost, especially for the robust analysis process. Therefore, a two-level solution strategy, an adaptive least square support vector regression model, and a novel dominant judging condition are skillfully employed to realize the tradeoff between the computation cost and accuracy of the robust design optimization algorithm. To verify the effectiveness of the proposed method, the fluctuation and distribution of electromagnetic performance of the robust motor design are analyzed and compared with those of a deterministic motor design. Finally, a prototype of the hairpin winding permanent magnet motor is manufactured and tested to further confirm the validity of the proposed method.

In order to accurately calculate the efficiency of electric vehicle drive motors in the full speed range during the design phase, this paper proposes a comprehensive motor loss fast calculation method. Firstly, a high-fidelity joint simulation model of control and design was established to simulate the real excitation sources in actual operation. Secondly, detailed modeling was conducted for each loss. Regarding iron loss, this paper considers the effects of PWM harmonics, as well as cutting, welding, and other processes, on the loss based on finite element calculations. This paper proposes a semi-analytical AC copper loss calculation method, which superimposes the effective section and end winding separately. A fast improvement simulation method is proposed for the eddy current loss of permanent magnets, which equivalently combines 2D finite element and 3D finite element, while considering factors such as segmentation. Finally, a loss separation scheme was designed and experimentally verified for each loss and motor efficiency, proving that the efficiency calculation error of most operating points was less than 1.5%.

In the context of high-power-density applications, oil-cooled motors have emerged as a research focus due to their superior cooling performance. The optimized design of cooling structures and the development of fluid analysis methods are crucial for improving overall system performance. In this study, a composite oil-cooled structure with concentrated flat-wire windings is proposed to enhance heat dissipation capability. Based on this configuration, an innovative hydrodynamic modeling approach for the stator and rotor oil channels is developed, effectively addressing the low efficiency of conventional finite element simulations. Using the proposed modeling method, the internal flow nonuniformity of the oil-cooled motor is analyzed, revealing the mechanisms by which key structural parameters affect heat transfer nonuniformity. Finally, experimental results demonstrate that the proposed model provides accurate flow rate predictions. The prototype achieves a continuous current density of 33.6 A/mm2, with a peak motor temperature of $130~^{\circ }$ C—representing a 60.7% improvement compared to conventional oil-cooling solutions.