| The permanent magnet coupling is based on the magnetic field generated by the permanent magnet,and uses the magnetic force between the permanent magnet or the induced magnetic field between the permanent magnet and the conductor to transmit the torque between the driving part and the driven part.Compared with traditional transmission equipment such as rigid couplings or flexible couplings,hydraulic couplings,etc.,it is more reliable,stable,economical,energy-saving and environmentally friendly,and has better controllability,which has obvious advantages.Its special non-contact transmission characteristics,as well as excellent performance such as speed regulation,soft start and overload protection,have also brought new options for mining transmission equipment,and have attracted widespread attention in the field of electromechanical transmission in coal mines.Permanent magnet coupling can be divided into disc permanent magnet coupling(DMPC)and cylinder permanent magnet coupling(CPMC)according to their structure.At present,in China,the application and research of permanent magnet couplings for mines mostly focus on DPMC and research of CPMC are relatively.Therefore,to fill the gaps in the research,promote the localization of permanent magnetic couplings,and aid with safe and efficient production in underground coal mines,there are important theories and engineering significance for the development of CPMC.In this thesis,a theoretical calculation model is established for the cylindrical permanent magnet coupling,and its working characteristics are studied.Based on the electromagnetic theory,the relationship equation between the magnetic flux density and the magnetic field strength at the working point of the permanent magnet is derived through the hysteresis loop and the material characteristics of the permanent magnet;the equivalent magnetic circuit method and the equivalent surface current are used The magnetic field induced by the permanent magnet and the conductor is equivalent to the magnetomotive force series magnetic resistance;the magnetic field division method is used to divide the air gap magnetic resistance into different magnetic flux tubes,and then calculate the magnetic resistance of each magnetic flux tube.Based on the reasonable division of the external magnetic circuit,an equivalent magnetic circuit model was established,and the relationship between the characteristics of the external magnetic circuit and the characteristics of the permanent magnet was obtained according to Kirchhoff’s law of the magnetic circuit,and the relationship obtained was restored to the permanent magnet.The curve equations are combined,and the analytical expression of the magnetic flux density of each magnetic flux tube is calculated,and the magnetic flux of each magnetic flux tube of the magnetic circuit is further calculated;combined with the skin effect of the conductor,according to the principle of Faraday electromagnetic induction,each magnitude of the ampere force that the magnetic flux tube magnetic field interacts with the conductor,and the resultant force of the tangential component force of each flux tube ampere force along the circumference is calculated,the theoretical calculation model of the cylindrical permanent magnet coupling is established,and the relationship between slip and torque is obtained by the relationship equation.A calculation program was written,a set of prototype calculations were performed,and the slip torque relationship curve of the CPMC was obtained.The finite element analysis software ANSYS Electronics was used to perform finite element analysis on the CPMC.After simplification within a reasonable range,an analysis model was established,and the part parameters and materials in the model were set up according to the actual situation,the boundary conditions and excitations are set reasonably,and then the finite element model is meshed.Set the slip and mesh length as variables,perform finite element simulation on the three-dimensional transient electromagnetic field of the CPMC.The simulation calculates the transmission torque under different slips,and further obtains the different curves of torque with slip under different meshing lengths;combined with the electromagnetic field analysis results,use ANSYS Workbench to further simulate and calculate the temperature field change of the CPMC.With reference to the existing experimental platform,the deficiencies were improved,and a new experimental platform was built after adapting the structural parameters and experimental requirements of the CPMC;the mechanical characteristics,start-up experiments,stable conditions experiments,and overload conditions experiments of the CPMC were carried out through experiments paltform.The experimental data is compared with the theoretical and simulation data to verify the accuracy of the theory and simulation.It is known that the error of the theoretical calculation result meets the requirements of the engineering calculation,but the simulation The accuracy of the result is higher.Combined with the theoretical calculation model and simulation results,the performance changes of the CPMC under different air gaps between the permanent magnet and the conductor,different materials of the conductor tube,and different magnetic materials are analyzed.Through the analysis and experiment of the prototype,the slip torque relation curve of the CPMC is obtained.From the curve,it is known that the slip is positively correlated with the transmission torque in the range of 0-800 rpm and is negatively correlated when it exceeds 800 rpm.The mechanical characteristics can be obtained from the relationship characteristics of the slip torque.The instantaneous slip rate of the CPMC is 1,and the torque currently is the starting torque.When the load torque is greater than the starting torque,the CPMC cannot start;the electromagnetic torque of the permanent magnet coupling increases with the increase of the load speed.The increase of the speed after the critical speed will cause the reduction of the electromagnetic torque,and the load will rotate when the load torque is reduced to the same.The torque is balanced with the electromagnetic torque,and the system enters a stable operation state.In-depth understanding of the soft start and overload protection characteristics of the CPMC through experimental research: both the coupling start and decoupling start of the CPMC have the soft start effect.In the prototype test,the decoupling start is compared coupling start,the motor start time is reduced by 32%,the peak current is reduced by 34%,and it has better soft start performance.The CPMC has an overload protection effect.The motor power supply should be cut off or the coupling of the CPMC should be disconnected as soon as possible after a locked rotor to ensure that the permanent magnet will not overheat and fail.In addition,appropriately reducing its locked rotor torque can improve the protection effect of the motor.The power consumption of the quadratic load is proportional to the third power of its speed.Therefore,the speed regulation function of the CPMC has an energy-saving effect for the quadratic load.When the motor is a six-pole pair motor with a rated speed of 1000 rpm,the prototype of CPMC can save up to 27% of energy consumption through speed control. |
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