Study On Electromagnetic Field Characteristics And Speed Regulation Performance Of Magnet Rotation-type Axial-flux Magnetic Coupler

Magnet Rotation-type Axial-flux Magnetic Coupler(MRAMC)is a new transmission device based on the principle of electromagnetic induction,which has the advantages of energy saving,vibration isolation and overload protection.The control of rotation of permanent magnets(PMs)is combined with the adjustment of the air gap thickness to achieve a large speed range when the MRAMC is applied to pumps and fans for speed regulation.Therefore,the research on the MRAMC has a practical value in engineering.In this paper,the research on the MRAMC mainly focuses on as follow:Firstly,the magnetic vector potential method that introduces induced magnetic field and the method of multiple harmonics superposition are combined for theoretical analysis and numerical calculation of electromagnetic torque and induced air gap magnetic field of MRAMC.The analytical model of the coupler is established,then the magnetic vector potential of each layer is obtained according to the boundary conditions of different layers,which is used to express the induced current of the conductor.The induced current path in the conductor is equivalent to elliptic coils equal to the number of PMs,then Biot-Savart Law is used to achieve the induced magnetic field distribution in the air gap under the 1st,3rd,and 5th harmonics of PM magnetic field.The induced air gap magnetic flux density and PM magnetic flux density are numerically calculated to obtain the transient air gap magnetic density.The final electromagnetic torque can be calculated with 3-D correction factor.Secondly,the distribution of static magnetic field,transient magnetic field and induced magnetic field,static magnetic flux and transient magnetic flux of MRAMC are simulated and analyzed.The 3-D distribution of the axial and circumferential static magnetic fields at different air gap thicknesses and different rotation angles of PMs are obtained,it is shown that the rotation of PMs affects the magnetic flux density waveform while the air gap thickness only affects the magnetic flux density amplitude.With the decrease of air gap thickness and rotation angle of PMs,the axial magnetic flux density amplitude is increasing by analyzing the axial transient magnetic field distribution.In addition,there is a nonlinear relationship.By analyzing the magnetic density amplitude under constant torque load conditions,it is shown that the larger the torque,the greater the amplitude.By analyzing the distribution of the induced magnetic field,it is concluded that there is a phase difference between the induced air gap magnetic field and the original magnetic field.By analyzing the distribution of magnetic flux at different air gap positions under static and transient conditions,the relationship among the magnetic flux,rotation angle of PMs and slip of is studied.Thirdly,the speed regulation performance of MRAMC is studied,then the speed regulation performance of three speed regulation modes under three load conditions is obtained.The speed regulation performance under constant torque load conditions is analyzed,then equal torque curves are proposed.The speed regulation performance under variable torque load conditions is analyzed,it is shown that speed regulation range increases first and then decreases with the increase of variable load coefficient.The speed regulation performance under constant power load conditions is analyzed,then the distribution diagram of the maximum power value is obtained.The starting process under constant torque load and variable torque load is analyzed.The axial force at different air gap thicknesses and different rotation angles of PMs is analyzed,with the increase of slip value,the axial force changes from magnetic pull to magnetic push.The relationship among air gap thickness,rotation angle of PMs and slip value is furthermore analyzed when the axial force is 0N.Finally,the theoretical torque of MRAMC are tested.The transmission performance and speed regulation performance of the magnetic coupler are tested on the constant torque load test platform,it is shown that the relationship between the air gap thickness and the electromagnetic torque at a certain slip value and mechanical characteristic curves are obtained.The comparison shows that the test value agrees well with the results obtained from the theory and simulation.