Study On Eddy Current In Discal Magnetic Driver

According as the basal theory of modern magnetism ,the magnetic driving is a new technology which realizes the contactless transfer of force or torque (power) by the magnetic force function produced through permanent magnet material or electromagnet .The equipment which can achieve the technology is named magnetic driver or magnetic transmission device, magnetic coupling and so on . With the magnetic driver in the industrial application of the gradual promotion, people driver to improve its efficiency with higher requirements. Scientific computing and control the eddy current in the magnetic driver, can effectively improve the transmission efficiency of the magnetic driver .The essential different between the magnetic driving and mechanical driving is that magnetic force driving transfer the torque using the thin wall of distance sleeve or the working clearance produced while magnetic field permeate magnetic circuit when it transfer torque and force to driving parts .For example the magnetic force driving pump and stirred autoclave are taken the seal gland driven by magnetic force instead of traditional shaft contacted kinematical seal equipment adopted by mechanical pump and kettle .At the same time it change kinematical seal to static seal.So the leak produced in the sealed place of transmission shaft is eliminated radically and the problems such as spill ,emiting ,dripping ,leak and the heat and abrasion of mechanical seal being in the equipments like industrial pump and kettle are solved .All of these create qualifications for transportation safely or the agitation of mediums like being poisonous in reaction ,flammable ,easy-explosive,corrodent and valuable .Now the main problems existed in the technology of magnetic force driving are the lifetime of bearing ,vortex ,high temperature and monitoring .The issue of vortex on magnetic driver has been investigated by many scholar but there are few people research on discal magnetic driver which is being vortex analysis in the paper .Discal magnetic driver is composed of inside and outside magnetic rotor and distance sleeve .Both the inside and outside magnetic rotor are made up of permanent magnet which is axial-magnetization and has been charged magnetism in opposite directions .The permanent magnet is arrayed alternately along the circumference in term of different polarities and fixed on yoke iron of mild steel to form siamesed magnetic open circuit .The distance sleeve is an important part of magnetic seal gland .If it is made of metallic material ,the metallic distance sleeve is in the alternating magnetic field whose direction and size change as specifically rule quickly when the inside and outside magnetic rotor do isochronous whirligig .In other words ,the flux in the thin wall of distance sleeve changes as time ,which will produce eddy current changed along the flux , current ring .The eddy current can heat permanent magnet and result in part irreversible demagnetization .So it is necessary to analyse the eddy current of magnetic force driver .The eddy current in the distance sleeve is arosen by the variational magnetic field ,so the research on the distributing and rule of magnetic field in the distance sleeve is the precondition to the study on the problem of eddy current in magnetic force driver .The basal theory of electromagnetic field is the springboard of this paper .Firstly ,the magnetic field of disk magnetic force driver is analysed by the numbers using the analytic method and finit element method .Then the farther analysis of the problem on the eddy current in the distance sleeve is done after getting the correct conclusion.The detailed content is as follows :(First).The theory of magnetic phenomenon is researched based on mass literatures of magnetism and magnetic force driving .The ultimate principle and character of the technology on magnetic force driving are introduced concisely .The developed history and actuality ,the key and developed orientation of the technology on magnetic force driving and the character of magnetic driver are analysed in a round .(Second). Firstly ,the structure and working mechanism of the magnetic driver are expatiated .Then the vocabulary of terms often used in magnetic driver are introduced .At last ,the problem of eddy current being attention to the research on magnetic driver is discussed amply .All of these become the theoretical basis in the research on the eddy current of the discal magnetic driver .(Third).Two equivalent models of permanent magnet ,namely ,equivalent electrical current model and equivalent magneticcharge model often used in the theoretical arithmetic of electromagnetic field are introduced amply.The formula of theoretical arithmetic on air-gap field of magnetic force driver is deduced applying on equivalent electrical current model and based on the model of disk magnetic force driver researched in the paper.Then the formula of theoretical arithmetic is solved in MATLAB and the influence on air-gap field caused by the parameters such as the thickness of magnetic rotor ,the radius of magnetic rotor ,the thickness of air-gap is analysed .The three-dimensional model in finite element of the magnetic field of the discal magnetic driver is created by the soft of the finite element and the arithmetic solution of air-gap field is solved .The correctness of the formula of theoretical arithmetic built in the paper is proved when the results of finite element and theory are contrasted in a suitable bound .Then the validity in the formula of theoretical arithmetic in the distributing of eddy current is ensured .(Four).Firstly the formulas of arithmetic in eddy current often used in projects are introduced in list,which supply theoretical bases for the analysis and controlling of the eddy current in the distance sleeve of discal magnetic driver .Then the formulas of theoretical arithmetic of the density distribution of the eddy current in the distance sleeve of discal magnetic driver with twelve magnetic poles is deduced based on the MAXWELL equation set of electromagnetic field and the formulas of arithmetic about the spoilage of the eddy current is obtained .After that ,the formulas of arithmetic is solved by MATLAB and the influence on the spoilage of the eddy current caused by the structural parameters of the magnetic driver is analysed .At last the planar model in finite element of the eddy current is created in the soft of the finite element aiming at the character of the discal magnetic driver and the influences on the distribution of the eddy current caused by the parameters of the distance sleeve such as the electric conductivity, magnetic conductivity and the rotate speed relativing to the magnetic rotor are analysed.The formula and result of theoretical arithmetic in the paper are proved to be right when the results in finite element and theoretical arithmetic are compared under six different speeds .The steps on reducing the spoilage of the eddy current in the distance sleeve is analysed aiming at the solved results.These supply theoretical help for the controlling on the spoilage of the eddy current and increase on the transmission efficiency of magnetic force. This paper analyses show that:reducing the pole radius, increasing material strength of isolation sets, reducing the materials conductivity and magnetic conductivity of isolation sets neither is impact the effective amplitude of the axial magnetic field of the magnetic driver and effectively reduce eddy current losses ,these works has a very important significance for the control eddy current losses of magnetic driver and increase the transmission efficiency of the driver in the future.