潜液式液化天然气泵用低温永磁同步电机研究现状综述

Review on Cryogenic Permanent Magnet Synchronous Motor for Submersible Liquid Natural Gas Pump

低温永磁同步电机具有高效率、高功率密度和运行稳定的优点,正在逐步替代低温感应电机,成为液化天然气泵用低温电机未来的发展趋势,但仍有一些关键技术问题有待解决。该文首先详细阐述了低温环境下永磁同步电机关键材料的电磁特性和机械特性的变化规律,明确了不同材料的选取原则。在此基础上,重点总结了低温永磁同步电机的设计方法、拓扑结构、多物理场耦合分析及控制策略等关键技术。然后,介绍了现有低温电机的制造工艺与测试方法,指出当前低温电机测试所面临的挑战和不足。最后,探讨了低温永磁同步电机领域亟待解决的关键技术问题,并对低温永磁同步电机的研究方向和发展趋势进行了展望。

A new global energy structure with oil,coal,natural gas,and new energy has developed.Natural gas is mainly stored and transported as liquefied natural gas(LNG).The submersible LNG pump plays an important role in the transportation and use of LNG,and the cryogenic permanent magnet synchronous motor(CPMSM)is the core driving equipment of the submersible LNG pump.This paper summarizes the key technical issues involved in CPMSM and provides a reference for future research and application.Firstly,the electromagnetic and physical characteristics of core materials,permanent magnet materials,insulation materials,and bearings used in CPMSM are reviewed in detail,clarifying the principles for selecting different materials.The stator and rotor cores can be made of oriented silicon steel sheets with high silicon content or amorphous alloy material to ensure the efficient and stable operation of CPMSM.The permanent magnet should use samarium cobalt permanent magnet material;multi-layer composite insulation material should be used for winding insulation;bearings can be low-temperature hybrid bearings,low-temperature all-ceramic bearings,and magnetic bearings.Secondly,according to the changes in the service characteristics of CPMSM materials in a cryogenic environment,the design methods of CPMSM based on multi-physics coupling analysis and analogy method are introduced.Compared to the conventional PMSM,the stator and rotor diameters of CPMSM can be reduced by 14.3%and 10.0%,respectively.In addition,from the perspective of reducing the losses of CPMSM and ensuring the structural strength of the motor,the stator and rotor topology structures of CPMSM are analyzed.Thirdly,the research on multi-physical field coupling analysis of CPMSM in recent years is summarized,focusing on the fluid-thermal field coupling analysis and stress distribution law of CPMSM under a cryogenic environment.Based on the characteristics of LNG flowing through CPMSM’s air gap,the effects of motor speed,LNG flow rate,and rotor surface roughness on rotor friction loss are analyzed.The advantages and drawbacks of three kinds of efficiency optimal control technology are discussed.Due to the difficulty in parameter measurement of CPMSM in cryogenic environments,the input power minimization strategy based on the search method has the advantage of independent motor parameters,which is suitable for CPMSM.Based on the investigation of the current CPMSM prototypes and commercial products,the manufacturing technique of CPMSM is summarized.The key parameters of CPMSM in a cryogenic environment,such as inductance,back EMF,shaft power,speed and torque,are difficult to measure directly.This paper introduces the existing testing methods of CPMSM for LNG pumps,analyzes its challenges and shortcomings,and discusses the solution of CPMSM testing technology in a cryogenic environment.Finally,this paper looks forward to developing trends for reducing the loss and temperature rise and improving efficiency and stability,including material service characteristics,optimization design methods,control strategies,testing methods,vibration and noise,and other high-efficiency cryogenic motors.Critical technical problems to be solved are also proposed,providing a reference for the research and development of CPMSM.