Research On Design Of Miniature Axial Flux Brushless DC Motor

Although the radial flux permanent magnet machine(RFPM)has been widely used for a long time,the inherent defects in structure make its application limited in special occasions.The emergence of new technology products and application requirements of special field put forward higher requirements on the structure and performance of the machine.At the same time,the discovery of new materials and the emergence of new technologies make it possible to create a new type of machine.Axial flux permanent magnet machine(AFPM)has advantages of compact structure,short axial dimension,high efficiency and high power density,etc.,especially in the situation of limited axial dimension.In this paper,a miniature axial flux brushless DC machine(AF BLDC)with single stator and single rotor is designed,and a prototype is developed to carry out experimental research.In this paper,single stator single rotor topology is selected based on the analysis of the existing topology of axial flux machine.The equivalent magnetic circuit model of the axial flux machine is proposed by using the method similar to the radial flux machine.The basic electromagnetic relationship of the axial flux permanent machine is deduced from the magnetic circuit model;finally the design of the windings and overall size of the machine are completed.After the size of the machine is determined,finite element analysis(FEA)of the model is launched by using ANSYS Maxwell.The axial force of axial flux permanent machine with single stator single rotor is very important to the design of bearing.The influence of air gap thickness,permanent magnet thickness and pole-arc coefficient on axial force and electromagnetic torque is studied in static magnetic analysis,which provides important reference data for follow-up bearing design.In transient analysis,the dynamic performance of the motor is simulated and analyzed by the method of field circuit coupling simulation.In this paper,Quasi-3D method is used to model and analyze the AFPM in order to solve the problem of large amount of finite element method(FEM).The quasi-3D modeling method is used to convert the axial flux permanent magnet machine into the linear motor model.And the analytical expression of the magnetic field of the axial flux permanent magnet machine is derived in Cartesian coordinate system by the research method of the linear motor.Then,cogging torque of the axial flux permanent magnet machine is deduced,with slot effect and end effect considered.Finally,the influence of fractional slot winding,pole-arc coefficient and slot width on cogging torque is analyzed and optimized design of groove width and pole arc coefficient is carried.In order to verify the correctness of theoretical analysis,a miniature axial flux brushless DC machine with single stator single rotor prototype is made by using split manufacturing method based on the analysis of the current processing technology.A test platform for axial force and motor performance is designed and built to carry out experimental research.The axial force measurement experiment,motor drive experiment and the motor efficiency curve measurement experiment are carried out respectively.The axial force measurement,motor no-load and load experiment are respectively carried out.After the analysis and comparison of the data,the basic data of the axial force and the dynamic performance of the motor are obtained.