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Rare‐earth permanent magnet synchronous machines face challenges in manipulating their magnetic fields, which hinders the ability to extend the operation speed range. Moreover, this inflexibility leads to reduced efficiency in high‐speed scenarios when the machine is under flux‐weakening control and increases the risk of the magnets becoming demagnetised. The authors propose an alterable‐magnetic‐circuit variable‐flux memory machine (AMC‐VFMM) and a multi‐objective hierarchical optimisation method is conducted to optimise the machine. Firstly, the topology and alterable‐magnetic‐circuit principle of the proposed AMC‐VFMM are introduced. Then, optimisation objectives including torque production capability, flux regulation capability, and resisting unintentional demagnetisation capability are defined, and the hierarchical optimisation approach is established by stratifying the optimisation objectives and variables through the sensitivity analysis. Finite element analysis indicates that electromagnetic performances of the optimised design scheme are significantly enhanced. The bench test of the prototype demonstrates the superiority of the proposed AMC‐VFMM and validates the effectiveness of the optimisation design method. [ABSTRACT FROM AUTHOR]

In order to accurately estimate the temperature rise for high‐power high‐speed permanent magnet machines (HSPMMs), a novel temperature calculation method considering the non‐linear variation of material properties with temperature is proposed based on multi‐physics co‐simulation analysis. According to the theory of computational fluid dynamics and heat transfer, the computation model of fluid–solid–heat coupling heat transfer is established, and the coupled field is calculated using finite volume method with fundamental assumptions and corresponding boundary conditions. With the influences from temperature gradient and water flow rate considered, the heat transfer coefficients of water pipe surfaces are obtained by the application of the inverse iteration method. Thus, HSPMM temperature and fluid field can be simulated numerically by the finite volume methods, while the spatial temperature distributions for the machine main components are analysed in this study. The 1.12 MW, 18,000 rpm HSPMM is prototyped with experiments conducted on it, while the test data are then compared with the calculated results, which validate the correctness of the solution method of the coupled field. [ABSTRACT FROM AUTHOR]

High‐speed permanent magnet motors (HSPMM) have attracted much attention due to the inherent characteristics such as high‐power density, small size, small inertia, and high response. HSPMM is a comprehensive and complex system of multidisciplinary cross‐coupling such as electromagnetism, structural mechanics, rotor dynamic, fluid mechanics and heat transfer. Therefore, the design of HSPMM requires a multidisciplinary and integrated design approach. In this study, a 20 kW, 20,000 rpm HS interior PMM (HSIPMM) is designed based on multi‐physics fields. To reduce the end length of winding, the back round winding type is adopted, compared with the common structure, it is found that the temperature rise of the stator used back round winding type can be reduced by 11.5%. Finally, the superiority of the proposed HSIPMM is proved by the experimental results, and the efficiency of the motor is about 96.1%. [ABSTRACT FROM AUTHOR]