Study On Dynamic Characteristics And Temperature Field Of Magnetic Gear With Halbach Permanent Magnet Array

Magnetic gear(MG)is a kind of transmission device which transfers motion and torque by coupling of magnetic field.It can realize contactless transmission,has the advantages of no friction,vibration isolation and noise reduction,no lubrication,overload protection and so on.In order to improve the transfer torque ability of magnetic gear,the Halbach permanent magnet array is introduced into the magnetic gear,and the magnetic field intensity of the working air gap of the magnetic gear is enhanced by using the one-side magnetic accumulation characteristic of the Halbach array,which makes the magnetic gear widely used in wind power generation,agriculture,water conservancy and other low-speed with high torque working environment.Therefore,the research of MG with Halbach permanent magnet array not only has high academic value,but also has great significance for engineering application.In this paper,the MG with Halbach permanent magnet array is studied in the following aspects:(1)The electromagnetic torque and loss of MG with Halbach permanent magnet array are analyzed and calculated theoretically.Firstly,the basic structure of MG with Halbach permanent magnet array and its three working modes are introduced,and the structural parameters of MG are defined.And then the magnetic field distribution in the air gap of the Halbach permanent magnet array is obtained by vector magnetic potential method and the boundary conditions of each region.By taking use of the analytical method the modulation effect of the magnetic pole plate is analyzed and the radial magnetic density distribution of inner and outer air gap and the output torque of inner and outer rotor are calculated by Matlab software.Finally,the theoretical analysis of the loss produced by the components of MG in stable operation are carried out and the theoretical formula of the loss are derived.(2)The influence of the size parameters of each component on the transmission performance of MG with Halbach permanent magnet array is studied by using Ansoft finite element software.Firstly,the finite element model is established according to the actual motion process of the magnetic gear.The thicknesses of the inner and outer air gap,the parameters of the regulating pole,the thicknesses of the permanent magnet and the logarithm of the permanent magnet pole in the inner and outer rotor are changed in turn by means ofcontrolling the variables.The effects of structural parameters on the output torque and torque density of magnetic gears are obtained.On the basis of selecting the appropriate structural parameters,the thicknesses of inner and outer air gaps are 1 mm,respectively the radial thickness of pole pieces are 4 mm,and the slotting ratio is 0.6,when the inner and outer air gap thicknesses are 1 mm,the radial thickness of magnetic pole plate is 4 mm,and the slotting rate is 0.6 mm.When the inner rotor permanent magnet thickness is 8 mm,the inner rotor permanent magnet pole pairs are 7 pairs,and the outer rotor permanent magnet magnetic pole pairs are 15 pairs,the MG not only has high output torque and torque density,but also improves the utilization rate of permanent magnet.(3)The static magnetic field distribution,air gap magnetic density,torque-angle characteristic,transmission performance,loss and efficiency of MG with Halbach permanent magnet array are analyzed.The static air gap magnetic field distribution of MG with Halbach permanent magnet array is simulated and analyzed by using Ansoft finite element software.The waveforms of inner and outer air gap magnetic density and the harmonic components in air gap are obtained.The torque-angle characteristic of magnetic gear is analyzed,the variation curve of moment-angle characteristic and the maximum static torque of inner and outer rotors are obtained.Under the condition of no load,sudden load,linear loading and overload,the changes of input and output torque and speed of MG are analyzed.When the load changes,the input and output speeds do not change,and the torque increases with the increasing of load.Based on the analysis of the loss characteristics of the whole MG and the components,and on the basis of the analysis of the influence of different input speeds on the loss of each component,it is concluded that the losses of the MG are mainly produced on the the magnetic regulating pole and permanent magnet of the outer rotor.With the increase of input speed,the losses of each component also increase.Finally,the influence of input speed and load torque on transmission efficiency is studied in the presence of loss.The results show that the transmission efficiency increases with the increase of load torque and decreases slightly with the increase of input speed.(4)The temperature rise characteristics of MG with Halbach permanent magnet array are analyzed.The heat source and heat transfer mode of MG are analyzed.It is found that the losses in MG are the main cause of temperature rise.The heat transfer is carried out by eachcomponent through heat conduction,heat convection and heat radiation.The temperature distribution of the whole MG and its components are simulated by ANSYS finite element software,and the influence of the change of input speed on the temperature of each part is studied.The results show that the temperature on the permanent magnet of pole pieces and outer rotor are higher than others.The temperature on the inner rotor is relatively low,and with the increase of the input speed,the temperature of each component increases accordingly.