High-speed permanent magnet synchronous machines (PMSMs) have attracted much attention due to their high power density, high efficiency, and compact size for direct-drive applications. However, the consequent power loss density is high, and hence heat dissipation is a major technical challenge. This is particularly the case for high-speed operation. In this paper, a MW level high-speed PMSM is designed and its electromagnetic and mechanical power losses comprehensively investigated using finite element analysis. The transient machine demagnetization performance is studied, and a composite rotor structure is proposed to improve machine antidemagnetization capability. The temperature distribution of the proposed high-speed PMSM is also analyzed using a fluid-thermal coupling method with calculated power loss. Experiments conducted on a prototype of the high-speed PMSM demonstrate the effectiveness of the numerical models developed and validate the results obtained.

For the high-speed permanent magnet synchronous motors (HSPMSMs), their magnetic fields are more complicated with the rotating magnetization and harmonics considered. Furthermore, there are interaction effects on motor iron loss from high frequency, temperature and compressive stress. In order to obtain the accurate HSPMSM iron loss calculation model, different iron loss models are proposed considering these physical factors, and the iron loss model considering the interaction effect of the multi-physics factors is given. The magnetic field, temperature field and stress field are analyzed for HSPMSM by FEM. Then the proposed models are employed to calculate the iron loss of the silicon steel sheet and the prototype. The accuracy of the proposed iron loss model, which can consider the interaction effect of the multi-physics factors, is verified by the experimental test measurements on the prototype.

High-speed permanent magnet machine (HSPMM) design is considered with particular attention paid to machine electromagnetic, thermal and mechanical analyses. In this paper, a 140 kW, 15000 rpm HSPMM is designed with its power losses evaluated at first. Then the machine temperature distribution is obtained based on Computational fluid dynamics (CFD) modeling. HSPMM is prototyped with experimental tests conducted to verify the calculation results. Mechanical strength analysis is performed for the HSPMM rotor structure with pole filler by Finite-element method (FEM) for the rotor at three operational conditions, while the influences from sleeve parameters on rotor strength are comprehensively studied for the HSPMM rotor at the most challenging condition. In this study, stator auxiliary slotting is extensively researched to reduce the rotor eddy current loss with little effects on machine output torque. The air gap flux density for HSPMM with auxiliary slotting is analytically predicted, while the working mechanism is illustrated in-depth. The effects from auxiliary slot dimensions, numbers and positions on machine performances are further proposed and investigated. The experimental tests also validate the reduction of HSPMM rotor eddy current loss by the application of auxiliary slotting.

The switched reluctance motor (SRM) benefits from its magnet-free nature, robust construction, low cost, flexible controls, and the ability to operate in harsh environments such as high temperatures and high pressure. It has received increasing attention for all-electric or multi-electric aircraft systems and electric vehicles (EVs) as compared with permanent magnet synchronous motors (PMSM) and other AC motors in some required high reliability and fault tolerance applications. However, the SRM is prone to considerable wind resistance due to the convex pole structure of the rotor during high-speed rotation, high torque ripple, and also vibration noise. Thus, it is currently a trending topic to develop special SRMs, tailored with high reliability and fault tolerance. Recent research demonstrates several promising feasible solutions to reduce torque ripples and enhance torque density and power factors, including changing topology of SRM, using advanced control methods, as well as different winding configurations. Among these options, the segmented switched reluctance motor (SSRM), as a deformation of the conventional topology, is shown to be capable of effectively optimizing the torque performance. Motivated by this advance, this paper aims to present a comprehensive literature review on the SSRM, first illustrating the development of the topology of the SRM, then providing a description as well as a classification according to the topology of the SSRM. In particular, we focus on the evolution of various kinds of segmental topology and improvement measures. Then, we discuss the performance, advantages, and disadvantages of various types of structures in terms of their electromagnetic aspects and their applications. Eventually, several promising future trends and application prospects of the SSRM are prospected, with the aim of shedding light on further research. In sum, the key contribution of this paper is to provide a valuable basis for detailed analyses of the structure and electromagnetic design of the SSRM that are expected to benefit future research.

This paper presents a research work on the electromagnetic loss modeling and demagnetization analysis for a high-speed permanent magnet machine (HSPMM). The iron loss is estimated by improved modeling considering harmonics and rotational magnetic field effects to achieve high precision; rotor eddy current loss is researched and comprehensively investigated using finite-element method (FEM). The auxiliary slot and PM beveling are also proposed to reduce the rotor eddy current loss for machine at high-speed operation. Temperature-dependent PM demagnetization modeling is utilized in HSPMM FEM analysis to investigate machine performance due to temperature variation, while optimized rotor structures are proposed and comparatively researched by FEM to improve the machine anti-demagnetization capability in harsh conditions. The HSPMM temperature is estimated based on the calculated loss results and machine computational fluid dynamic modeling. Experimental measurements on the prototype machine verify the effectiveness of the machine electromagnetic and thermal modeling in the paper.

High-speed permanent magnet synchronous motor (PMSM) is widely used in industrial applications because of the high-efficiency, but the disadvantages which limit its development are still severe, which include the low yield strength of permanent magnet material and the poor rotor dynamics performance, thus the stress and modal analysis of the high-speed rotor are important. The traditional multidisciplinary optimization numerical analysis of the different disciplines is too time-consuming because the optimization process requires multiple calls to the numerical models of the motor. Therefore, a multi-fidelity (MF) surrogate model is proposed to balance the accuracy and efficiency of the multidisciplinary optimization process, which uses the analytical models to establish the large low fidelity (LF) sample space and use numerical models to establish the small high fidelity (HF) sample space; then uses the hybrid sample space to train the surrogate models. And in order to reduce the total number of the sample points, a gradient sequential sampling is proposed. That sampling method can make the sampling process more efficient as well. After that, the multi-fidelity surrogate models are used to optimize the rotor system under the NSGA-II algorithm. Finally, a prototype is manufactured to verify the final optimal point.