Na Huang

The ferrite-assisted synchronous reluctance motor (FaSynRM) does not rely on rare earth permanent magnets. With its high efficiency and low cost, it has broad application prospects in the industrial field. However, the motor has a variety of rotor structures, which show different multiphysical field characteristics. Most of the existing research focuses on the electromagnetic characteristics analysis of a specific rotor structure, and lacks comparative research on different rotor structures, especially the analysis of demagnetization characteristics under high overload conditions, resulting in the multiphysical field characteristics of many rotor structures are still unclear. Therefore, this article focuses on the multiphysical field characteristics of different rotors, including antidemagnetization characteristics, electromagnetic properties, loss characteristics and temperature distribution. First, the 75 kW, 1500 rpm FaSynRM motors with four rotor structures are introduced, and the influence of main design parameters on electromagnetic performance is analyzed comprehensively. In addition, this article also carried out multiobjective optimization of these four rotor structures. Then, the motor performance of four rotor structure optimization schemes is compared, including antidemagnetization characteristics, electromagnetic performance, loss and temperature distribution. Finally, in order to verify the correctness of the theoretical analysis, a full-size model was manufactured and tested.

At present, there are many studies on reducing the amount of permanent magnets by using the permanent magnet assisted synchronous reluctance (PMa-SynR) rotor structure in the field of constant speed and high speed motors. However, the research on the application of PMa-SynR rotor structure in the field of low-speed high-torque permanent magnet motor (LSHTPMM) is missing. Therefore, the main purpose of this paper is to explore the application value of PMa-SynR rotor structure in the field of low speed and high torque, especially to explore whether the use of PMa-SynR rotor structure can greatly reduce the amount of rare earth permanent magnets. Firstly, according to the design and manufacture requirements, two 55 kW, 152 rpm LSHTPMMs with interior V-shaped rotor structure and PMa-SynR rotor structure are designed respectively, and the influence of design parameters of interior V-shaped rotor and PMa-SynR rotor on electromagnetic performance is analyzed. Secondly, the multi-objective optimization design of the two motors is carried out to obtain the optimal rotor design scheme of the two motors. Thirdly, the electromagnetic characteristics of the two optimized motors, the weight and cost of the permanent magnet materials and the temperature characteristics are compared and analyzed. Finally, two prototypes with different rotor structures were fabricated for experimental verification.

For high-power low-speed permanent magnet motors (LSPMMs), which are typically large in size and often subject to installation space constraints, the tangential rotor structure is more favorable than the radial surface-mounted permanent magnet (SPM) rotor design due to its ability to generate higher output torque within the same volume. An integrated tangential rotor structure that combines flux barriers with silicon steel laminations offers improved manufacturability and is more suitable for mass production. Nevertheless, current research lacks a comprehensive understanding of the design principles governing the integrated tangential rotor structure in LSPMMs. Therefore, this article focuses on the detailed design rules of the integrated tangential rotor structure for high-power LSPMMs, including different rotor structures, magnetic isolation characteristics, electromagnetic properties, and mechanical strength. First, based on a 1200-kW 75-r/min high-power LSPMM, two kinds of integral tangential rotor structures are proposed. On this basis, the influence of different pole–slot combinations and sizes of magnetic isolation bridges on electromagnetic performance is analyzed in detail. Second, multiobjective optimization and mechanical strength analysis of two kinds of tangential rotor structures are carried out. Then, the electromagnetic performance and material consumption of two rotor structures are compared. Finally, a full-size prototype is manufactured and tested to verify the theoretical analysis.

For high-speed permanent magnet motors, it is difficult to dissipate heat due to its small size, and excessive temperature would reduce the stability of the motor. Therefore, the cooling method of the motor is very important to the stability of the whole machine. However, the traditional cooling system of high-speed permanent magnet motors requires an additional fan or water circulating machine, which increases the volume and complexity of the whole system. Therefore, this article takes the self-fan cooling high-speed permanent magnet motor system as the research object and analyzes the flow rate generated by the centrifugal impeller inside the motor. On this basis, two kinds of internal air cooling paths are proposed and the influence of different design parameters on temperature characteristics is analyzed and compared in detail. A prototype is manufactured, and detailed electromagnetic and temperature rise experiments are carried out to verify the correctness of the theoretical analysis. This article provides a reference for the cooling scheme of high-speed permanent magnet motor.

There are three main types of winding structures for high-speed permanent magnet motors: double-layer lap winding, double-layer concentric winding, and toroidal winding. Different winding structures have different multiphysics properties. For example, although the toroidal winding can effectively improve the rotor dynamic characteristics, the loss and temperature characteristics would become worse. Unfortunately, current research on high-speed permanent magnet motors is mainly based on double-layer lap winding structures, lacking a comprehensive analysis of the multiphysical characteristics of the three winding structures. The quantitative impact of each winding structure on the various performance parameters of high-speed permanent magnet motors is unclear. Therefore, this article comprehensively compares the electromagnetic characteristics, loss characteristics, rotor dynamics characteristics, and temperature characteristics of three winding structures and finally obtains the quantitative impact of the three winding structures on various performance indicators.