Study On Adjustable-speed Performance And Smart Adjustable-speed System Of Axial-flux Asynchronous Magnetic Coupler

The axial-flux asynchronous magnetic coupler is a new type of power transmission device based on electromagnetic induction principle,which can realize non-contact transmission between the motor and load,and which is widely used in machinery,electric power industry,metallurgy and various departments because of many advantages such as vibration isolation,non-essential high precision alignment,light load starting,overload protection and so on.Also,the magnetic coupler can achieve adjustable-speed function by changing air-gap thickness under different load conditions,and realize energy-saving effect when dirving centrifugal fan,pump and other variable torque loads.So,the research on magnetic coupler is of great significance not only in the academic value,but also in the practical value.In this paper,the research on the axial-flux asynchronous magnetic coupler is as follows:(1)Calculation model for torque and adjustable-speed relationship of the axial-flux asynchronous magnetic coupler are derived.A magnetic coupler model is developed by equivalent magnetic circuit and Kirchhoff's law of magnetic circuit,and magnetic circuit parameters are figured out by analytical calculation of the model,then,the final torque expression is built by combining three dimensional correction coefficient and the torque formula.According to the different load conditions,the adjustable-speed relationship expressions of the coupler under constant torque loads and variable torque loads are deduced,furtherly,by using Matlab software,the calculated values of adjustable-speed relationship are obtained.(2)In order to analyse mechanical characteristics and adjustable-speed characteristics,a three dimensional finite element model of the axial-flux asynchronous magnetic coupler is built.A 3-D finite element model of axial-flux asynchronous magnetic coupler is established and the modeling process is described.Mechanical characteristics and adjustable-speed characteristics of coupler are simulated,and mechanical characteristic curves and adjustable-speed characteristic curves are achieved.Based on this,load capacity,speed regulation,energy conservation and starting performance of the coupler are analysed,as a result,the appropriate variable torque load coefficient and the way of improving the starting performance of the coupler are proposed.Adjustable-speed relationship of the coupler under different load torque is simulated,and the regulation between slip and air-gap thickness in the adjustable-speed process is achieved,which verifies the correctness of theoretical calculation on adjustable-speed relationship.(3)Overall scheme of smart adjustable-speed system is designed,and the whole transfer function of adjustable-speed system is established.Design scheme of smart adjustable-speed system is proposed,and mechanical structure model and control system diagram of smart adjustable-speed system are built.Then,the motion control scheme of adjustable-speed system and the hardwares of control system are determined,and the hardware wiring diagram is designed.In order to get the whole transfer function of adjustable-speed system,the transfer functions of mechanical structure and control system are researched.Furtherly,the relationship between input signal and air-gap thickness is determined,and the stability of smart adjustable-speed system is analysed by transfer function.(4)The prototype of the axial-flux solid asynchronous magnetic coupler is designed and manufactured,and the adjustable-speed performance test platform is built.Adjustable-speed relationship of the coupler under constant torque load and variable torque load,load characteristic of the centrifugal fan are tested.According to the results,slip of the coupler increases with the increase of air gap thickness,and the variable torque load coefficient of the centrifugal fan is determined.It has good consistency between test value,calculation value and simulation value.