Yanhong Chen

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.

In the optimization of high-speed permanent magnet motors (HSPMMs), electromagnetic characteristics, rotor stress, rotor dynamics, and temperature characteristics must all be considered simultaneously, and there are numerous optimization parameters for both the stator and rotor. These factors pose significant challenges to the multiphysics optimization of HSPMMs. Therefore, this paper presents a multiphysics optimization process for the HSPMM of 60 kW 30,000 rpm by combining subspace strategy and sequential strategy to mitigate the issues of high training volume and mutual coupling. Ten optimization parameters of stator and rotor are determined firstly. Then, using finite element analysis of rotor stress and rotor dynamics, the range of values for critical parameters of the rotor is established. Next, in the electromagnetic optimization, the process is divided into rotor parameter subspace and stator parameter subspace according to the subspace optimization strategy. The temperature field is also checked based on the optimization results. Finally, a prototype is manufactured and the comprehensive performance is tested to validate the multiphysics optimization process.

For high speed interior permanent magnet (IPM) motor, the measures to improve rotor strength inevitably affect electromagnetic, loss and temperature characteristics, which makes it difficult to judge which rotor structure is better in design. In this paper, four different rotor structures of high-speed IPM motors are compared comprehensively, including rotor stress, electromagnetic and loss characteristics, and temperature distribution. Firstly, four rotor structures of 140 kW, 18 000 rpm high-speed IPM motor are introduced, and effects of main factors on rotor stress and electromagnetic characteristics for four rotor structures are analyzed comprehensively. Secondly, the effect of manufacturing tolerances on rotor stress is also performed for four rotor structures. Thirdly, the design parameters of four rotor structures are optimized by considering rotor stress, electromagnetic and loss characteristics. Then, the multiphysics performance of the four rotor structures is compared, including the rotor stress, electromagnetic performance, loss and temperature. In addition, rotor mechanical strength at different surface linear velocities is analyzed by scaling up rotor outer diameters and rotor design parameters. Finally, to verify the theoretical analysis of this paper, two rotor structures are manufactured and tested for electromagnetic, rotor strength and temperature characteristics.

For low-speed permanent magnet motors (LSPMMs), the winding copper loss accounts for most of the total loss, which resulting in the winding to become the hottest spot of the entire motor. Excessive winding temperature would cause insulation damage or reduce the service life of the motor. Therefore, it is necessary to adopt efficient cooling methods to reduce the winding temperature. In this paper, two efficient cooling structures are analyzed: a high thermal conductivity path (HP) placed in the middle of the winding and the end winding potting. On the one hand, the influence of different factors on the temperature characteristics of each cooling structure is analyzed through 3D finite element analysis. On the other hand, based on the water-cooled structure and two efficient cooling structures, four cooling schemes are designed and their winding temperature distributions are compared, so as to obtain the effect of different cooling structures on winding temperature and the interaction between different cooling structures. Finally, two prototypes with different cooling structures are fabricated and the electromagnetic and temperature characteristics are tested to verify the theoretical analysis.