Design And Analysis Of Axial Flux Permanent Magnet Generator

China has put forward the strategic goals of "carbon peaking" and "carbon neutral".It promotes the development of clean energy generation technology in China,among which wind power generation technology is developing especially fast.Wind turbine is the core of wind power generation system,which is divided into horizontal axis wind turbine and vertical axis wind turbine.The vertical axis wind turbine is flat,with short axial dimension and simple structure.When the stator is a coreless structure,it can reduce the iron consumption of the generator and eliminate the cogging torque,and this structure has the advantages of high efficiency and low starting torque.However,the coreless structure of the stator will increase the equivalent air gap length of the generator,resulting in a larger leakage flux and thus affecting the generator performance.In this paper,the main initial parameters of axial flux permanent magnet generator(AFPMG)are determined according to the electromagnetic calculation method of conventional radial generator.The equivalent magnetic circuit(EMC)model is established according to the structural characteristics of the AFPMG,and it is proposed to compare the leakage flux path length to determine the leakage flux region and the leakage flux type,which solves the problem that the leakage flux is difficult to be determined as the generator size changes.The EMC method is used to solve for the permeance and obtain the expressions for the no-load leakage coefficient,air-gap flux and total flux.The effects of pole arc coefficient,air gap length and PM thickness on the no-load leakage coefficient and the effects of PM outer diameter,PM inner and outer diameter ratio,PM thickness and air gap length on its loss and efficiency are investigated,and the corresponding trend graphs are obtained.Based on this,the final parameters of the generator are determined and the generator performance is verified by the finite element method.Finally,the no-load air gap magnetic field,armature potential,no-load magnetic chain,electromagnetic torque,load current and voltage of the generator are solved by the EMC method and verified by the finite element method.A coreless AFPMG prototype was manufactured according to the design parameters,and an experimental platform was built.The generator was dragged by the prime mover to simulate wind power generation,and the prototype was tested at no load and load respectively.The results show that the output power quality of the prototype is high and the generator meets the design requirements.The experimental results are consistent with the results of the magnetic circuit method and the finite element method,which verify the correctness of the proposed magnetic circuit analysis method.