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

KOU Ziming; KOU Shaokai; WU Juan; WANG Yandong

doi:10.12438/cst.2025-1550

Abstract：The permanent magnet self-driven technology applied to rotating mechanical transmission systems can enhance the energy effi-ciency and performance of equipment.To enhance the transmission efficiency of small-power asynchronous motor drive systems in exist-ing mine hoists,a permanent magnet external rotor hoist integrating the drive unit and load has been developed.However,its highly integ-rated 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 struc-ture 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 perspect-ive,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 tech-nical 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 eccent-ric pole cutting and bidirectional non-magnetic fixing technology;Design methods for the permanent magnet edge structure and asymmet-ric 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 eccent-ric pole cutting+asymmetric rectangular slot"model can reduce torque ripple by 9％;② The causes of air gap variation include rotor de-formation and stator deformation.The former increases the amplitude of electromagnetic wave,while the latter generates high-order har-monics 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-demag-netization methods of permanent magnets,as well as the eddy current loss and temperature rise control of permanent magnets.Addition-ally,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 applica-tion prospects in ultra-deep well hoisting systems.Numerical simulation results indicate that when the hoisting height is 2 000 m,the max-imum effective load can reach 70 tons.