Research On Characteristics Of AC Permanent Magnet Motor In Extreme Environment

Extreme environment AC permanent magnet motor(PMAC)is a key core component of deep space,deep sea and deep ground equipment,and it works in extreme environment with wide-range temperature and pressure.Extreme environment changes material properties,physical field is complex,coupling is serious,nonlinear problem is prominent,and characteristics and output capacity have changed significantly.Lack of in-depth systematic research on key issues has led to lack of theoretical and technical support for design,analysis and application of extreme environment motor,which has severely restricted technology development.The paper studies key issues of material characteristics acquisition,comprehensive physical field calculation,characteristic analysis and parameter design.Aiming at problem of material characteristics in extreme environments,material characteristics test method is studied,and change law is revealed.An extreme environment simulation device for temperature and pressure coupling has been constructed,which simulates environment for deep space,deep sea and deep ground exploration.Measurement methods of magnetization characteristics,loss characteristics and conductivity characteristics of electrical steel,demagnetization curves of PM materials,and conductivity characteristics are proposed to solve problem of limited test space,difficulty in magnetic field construction,contact potential and contact resistance affecting accuracy.Aiming at structure and stress of stator core,a characteristic measurement method is proposed for testing electrical steel ring specimen and strip specimen respectively,which truly reflects characteristic changes caused by stress on yoke and teeth of stator core.Through testing different specifications of materials,it reveals characteristics changing laws of electrical steel and PM materials in extreme environments.Research results show that both high temperature and low temperature lead to changes in permeability of electrical steel,while loss decreases with temperature increase;high pressure reduces magnetic performance of electrical steel and loss increases;magnetic properties and conductivity of PM materials are affected by temperature obviously,pressure influence is small.It is discovered that magnetization state has different effects on conductive properties of Sm₂Co₁₇ and Nd Fe B.Aiming at extreme environments with large-scale temperature changes such as deep space,calculation and characteristic analysis of physical field are carried out,revealing effect of temperature on motor physical field and characteristics.A multi-physics field coupling calculation method based on temperature characteristics of materials is proposed,which comprehensively considers strong coupling of electromagnetic field and temperature field in PMAC,and establishes a multi-physics field coupling calculation model.On the basis of physical field calculations,effect of temperature on motor characteristics is calculated and analyzed.Through physical field calculation and motor characteristics analysis,effect of temperature on loss,temperature rise,motor characteristics and design parameters is revealed.Taking allowable limit temperature,effect of temperature on motor output capacity is analyzed.The results show that iron loss decreases with temperature;low temperature causes torque fluctuation to increase and efficiency decrease;temperature has a significant impact on motor output capacity.Aiming at extreme environment of deep-sea motor with internal oil filling,internal and external pressure balance,and pressure range variation,the physical field calculation and characteristic analysis are carried out,and effect law of pressure on motor physical field and characteristics is revealed.The interaction and effect mechanism of electromagnetic field,temperature field,fluid field and stress field in PMAC are analyzed.Considering relationship between magnitude,distribution and direction of stress generated by pressure on stator core and magnetic field,a modeling method is proposed to describe characteristics of stator core yoke and tooth materials.Ring electrical steel sample is used to describe yoke material characteristics,and strip sample are used to describe tooth material characteristics,which truly reflects effect of pressure on material characteristics.Based on calculation of stress field,electromagnetic field,fluid field and temperature field,effect of pressure on motor characteristics is calculated and analyzed.It reveals effect of pressure on loss,temperature rise and motor characteristics,and design parameters.Taking the allowable limit temperature,effect of pressure on motor output capacity is analyzed.The results show that increase in pressure will increase iron loss,reduce cogging torque and average torque,reduce efficiency,and soften mechanical characteristics.Aiming at temperature and pressure coupling extreme environment,multi-physics field coupling calculation and motor characteristics analysis are carried out,and effect law of temperature and pressure coupling on physical field and motor characteristics is revealed.Based on separate effects of temperature and pressure,multi-physics field coupling relationship under temperature and pressure coupling is analyzed,and a physical field model that comprehensively considered temperature and pressure coupling is established,and comprehensive physical field calculations are carried out based on physical field calculations.The calculation and analysis of PMAC loss and characteristics under temperature and pressure coupling,as well as effect of environment on design parameters and limit output capacity.The results show that temperature and pressure coupling will cause output torque to decrease,efficiency is reduced,and mechanical characteristics become soft.Temperature and pressure have a certain offsetting effect on the iron loss and oil friction loss.Aiming at problem of difficulty to apply load and separat loss in extreme environment motor test,extreme environment PMAC experimental method is studied.Designed and manufactured a dual-motor coaxial structure experimental device,proposed extreme environment iron loss,oil friction loss separation and motor characteristics measurement methods.Through electromagnetic equivalence and rotor interchange tests,the problems of no load and sensor availability,mutual effect of losses in extreme environment motor experiment are solved.Iron loss,oil friction loss,efficiency characteristics,temperature rise and mechanical characteristics are measured and analyzed,which verified rationality of calculation of physical field characteristics and motor characteristics.