The effects of multi-phase and multi-layer windings of the 12-slots 10-poles surface-mounted permanent magnet synchronous machines (SPMSMs) on eddy current losses in permanent magnets (PMs) are mainly investigated using the 3-D finite element analysis in this paper. Eddy current losses in PMs considering its axial segmentation are also analyzed. It is demonstrated that dual three-phase four-layer (DTP-FL) winding layout has the minimum value of eddy current losses in PMs, when segmentation number $N = 4$. It is because DTP-FL winding has smaller magnitude of high-order magnetomotive force harmonics relative to other four winding layouts. The average torque and torque ripple changing with multi-phase, multi-layer, and axial segmentation are also studied. Finally, the no-load and load experiment platform for an axial flux integrated-starter generator with DTP-FL winding and radial segmented PM are established in order to validate the proposed method under power generation mode.

The interaction between the permanent magnets and the armature teeth of the PMSM generates cogging torque. It causes vibration and noise. Therefore, this paper establishes the analytical formula of the cogging torque of the motor with auxiliary slots on the surface of the rotor. It shows that reasonable slots can weaken the cogging torque. But it’s essential to determine whether the air-gap flux density harmonics will increase appreciably by slotting. A V-type IPMSM with 8-pole, 48-slot is modeled to analyze the cogging torque. Two new rotor slot shapes—inwardly biased slots and outwardly biased slots—are proposed and researched to reduce the cogging torque of the V-type IPMSM. And they are compared with the traditional symmetrical auxiliary slots. Research shows that the inwardly biased slots and the symmetric auxiliary slots can obtain a better effect on the cogging torque than the outwardly biased slots. By the symmetrical auxiliary slots, the cogging torque is weakened by 75.88%, but the torque ripple increases from 22.36% to 29.60%. By the inwardly biased slots, the cogging torque is weakened by 75.64%, and the torque ripple drops from 22.36% to 12.95%. The inwardly biased slots could successfully suppress the torque ripple.

This study proposes an improved decoupled model of mutually coupled dual‐channel switched reluctance machine (DCSRM) based on the equivalent inductance and flux linkage characteristics that consider magnetic saturation in dual‐channel operation (DCO) mode. A three‐dimensional finite‐element analysis (FEA) is used to calculate the static phase equivalent inductance of DCSRM for the simultaneous two‐phase excitation with consideration of saturation. And an indirect experimental test is performed to measure the equivalent flux linkage under the simultaneous two‐phase excitation and compared with the FEA results. In this improved decoupled model, the phase equivalent inductances and flux linkages in each channel are independent to each other and separately expressed as a function of rotor position and their own phase current. The static magnetic characteristics, details of modelling procedure and performances prediction for the DCSRM under DCO mode without and with consideration of saturation are compared. Finally, an experimental set‐up for a 12/8 DCSRM drive system based on dSPACE is built and the simulation and experimental results are compared, which verifies high accuracy of this improved modelling method.

The recent development of micro-fabrication technologies has provided new methods for researchers to design and fabricate micro metal coils, which will allow the coils to be smaller, lighter, and have higher performance than traditional coils. As functional components of electromagnetic equipment, micro metal coils are widely used in micro-transformers, solenoid valves, relays, electromagnetic energy collection systems, and flexible wearable devices. Due to the high integration of components and the requirements of miniaturization, the preparation of micro metal coils has received increasing levels of attention. This paper discusses the typical structural types of micro metal coils, which are mainly divided into planar coils and three-dimensional coils, and the characteristics of the different structures of coils. The specific preparation materials are also summarized, which provides a reference for the preparation process of micro metal coils, including the macro-fabrication method, MEMS (Micro-Electro-Mechanical System) processing technology, the printing process, and other manufacturing technologies. Finally, perspectives on the remaining challenges and open opportunities are provided to help with future research, the development of the Internet of Things (IoTs), and engineering applications.

A high-efficiency thermal management system is one of the key points in the practical application of electromagnetic rail launcher (ERL). In this paper, the thermal characteristics in ERL with the section of rectangle, convex, and concave rails by active cooling under different friction coefficient condition are investigated. By two cooling approaches, at two launch rates, with four friction coefficients, peak temperature in convex rails at the same moment is minimum in three types rails. Joule heat dominates in three shapes rail by channel or surface/channel cooling approach, but friction heat is a nonnegligible part under multiple launching mode. The spatial and temporal distribution features of peak temperature of three shapes rail with different friction coefficient under active cooling condition are compared. The mathematical relations between friction coefficient, time and temperature rising caused by friction at pulse end time and shot end moment in ERL with the three types rail are obtained, respectively. In terms of obtaining lower maximal temperature in rail, the ERL with convex rails is the best one.