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永磁外转子矿井提升机多物理场耦合研究进展

Research progresses on multi-physical field coupling analysis of permanent magnet external rotor mine hoist

  • 摘要: 旋转机械传动系统永磁自驱化可促进装备的节能增效,为提高现有矿井提升机中小功率异步电机驱动系统的传动效率,研发了集驱动单元与负载为一体的永磁外转子提升机。但高度集成化的特点也使径向时变大载荷直接作用于滚筒外表面,带来了2个技术难题:① 永磁体边缘切削加剧齿槽转矩问题,大直径滚筒内壁需要轴向分段布置大量永磁体,并与多个定子槽相配合,具有高功率密度的拓扑结构设计不仅密切关系着驱动系统的效率和成本,而且能够有效抑制由磁场能量变化引起的齿槽转矩和转矩脉动;② 气隙变化引起机械−电磁耦合振动问题,动载荷会引起承载面的局部变形,导致永磁体与定子外圆之间的气隙产生非均匀变化,加剧磁场畸变,诱发严重的机械−电磁耦合振动,需要从动力学的角度揭示气隙变化对振动的影响机理,有助于“对症下药”探索抑制方法。首先,综述了矿井提升机传动方案的发展历程,引出“无减速器、无高速轴、无联轴器”的永磁外转子提升机,并分析了该方案相较于三相异步电机驱动方案的主要优势。然后,重点阐述了永磁外转子提升机拓扑结构设计、动力学分析和永磁体磁性能影响因素3个方面的技术现状,包括外极弧偏心削极永磁体、永磁体边缘结构和非对称定子槽结构设计方法,气隙变化规律和机械−电磁耦合振动特性分析方法,以40极168槽单绳缠绕式永磁外转子提升机为例,基于有限元分析和现场试验相结合进行验证,结果表明:① “倒角形边缘外极弧偏心削极永磁体+非对称定子槽”模型可以降低转矩脉动9%;② 气隙变化的诱因包括转子变形和定子变形,前者会增大电磁力波的幅值,后者则会在电磁力波的主谐波附近产生阶次为±2和±4的高次谐波。在永磁体磁性能影响方面,主要对永磁体退磁特性以及防退磁方法、永磁体的涡流损耗和温升控制2个方面展开论述,展望了永磁外转子提升机在永磁体磁性能方面的研究内容。最后,探讨了双绳缠绕式永磁外转子提升机的布置方案,以及在超深井提升系统中的应用前景。数值模拟结果表明,提升高度为2 000 m时,有效载荷最大可达70 t。

     

    Abstract: The permanent magnet self-driven technology applied to rotating mechanical transmission systems can enhance the energy efficiency and performance of equipment. To enhance the transmission efficiency of small-power asynchronous motor drive systems in existing mine hoists, a permanent magnet external rotor hoist integrating the drive unit and load has been developed. However, its highly integrated nature exposes the external surface of the drum directly to large radial time-varying loads, leading to two key technical challenges: ① The edge cutting of permanent magnets exacerbates the cogging torque issue: the inner wall of the large-diameter drum requires axial segmented arrangement of a large number of permanent magnets, which must be matched with multiple stator slots. The topological structure design with high power density is not only closely related to the efficiency and cost of the drive system but also effectively restrain the cogging torque caused by changes in magnetic field energy; ② Mechano-electromagnetic coupled vibration induced by air gap variation: dynamic loads cause local deformation of the bearing surface, resulting in non-uniform variations in the air gap between the permanent magnets and the external circle of the stator. This exacerbates magnetic field distortion and triggers severe mechano-electromagnetic coupled vibration. It is therefore necessary to reveal the mechanism by which air gap variation affects vibration from a dynamic perspective, which will facilitate the targeted exploration of suppression methods. First, this study reviews the development history of transmission schemes for mine hoists, introduces the permanent magnet external rotor hoist featuring "no reducer, no high-speed shaft, and no coupling," and analyzes its main advantages over the three-phase asynchronous motor drive scheme. Subsequently, it focuses on elaborating the technical status quo from three aspects: the topological structure design, dynamic analysis of the permanent magnet external rotor hoist, and the influencing factors of the magnetic properties of permanent magnets. This includes: The permanent magnet with external pole arc eccentric pole cutting and bidirectional non-magnetic fixing technology; Design methods for the permanent magnet edge structure and asymmetric stator slot structure; Analytical methods for air gap variation laws and mechano-electromagnetic coupled vibration characteristics. A 40-pole, 168-slot single-rope winding permanent magnet external rotor hoist is taken as an example for verification through a combination of finite element analysis and on-site tests. The results show that: ① The “chamfered-edge permanent magnet with external pole arc eccentric pole cutting + asymmetric rectangular slot” model can reduce torque ripple by 9%; ② The causes of air gap variation include rotor deformation and stator deformation. The former increases the amplitude of electromagnetic wave, while the latter generates high-order harmonics with orders of ±2 and ±4 near the main harmonic of the electromagnetic wave. Regarding the influencing aspects of the magnetic properties of permanent magnets, the discussion mainly focuses on two dimensions: the demagnetization characteristics and anti-demagnetization methods of permanent magnets, as well as the eddy current loss and temperature rise control of permanent magnets. Additionally, it looks ahead to the research content of permanent magnet external rotor hoists in terms of the magnetic properties of permanent magnets. Finally, the study discusses the layout scheme of the double-rope winding permanent magnet external rotor hoist and its application prospects in ultra-deep well hoisting systems. Numerical simulation results indicate that when the hoisting height is 2 000 m, the maximum effective load can reach 70 tons.

     

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