| A concentric magnetic gear with Halbach permanent-magnet arrays, whose input sides isphysically isolated with the output sides, transfers torque by magnetic field, it has many merits,for example: high torque density, efficiency and high overload protection and so on. Such innerand outer rotor’s magnetic gear adopts concentric structure, which effectively improves theutilization of the permanent magnet. Its torque density and efficiency are higher than traditionalstructures’; therefore, it has better prospects.This project is one part of the National Natural Science Foundation of flux decoupling-typemagnetic variable speed permanent magnet brushless motor (51177097), and its purpose is toresearch on the new structure of the magnetic transmission.In this thesis, the works focus on an exact analytical method for a concentric magnetic gearwith Halbach permanent-magnet arrays, and the main works include the following ones:Firstly, an exact2-dimensional analytical method is used to calculate the magnetic fielddistribution in a concentric magnetic gear. The analytical method is based on the resolution ofLaplace’s and Poisson’s equations for each sub-domain, i.e., inner and outer permanent magnetrotors, inner and outer air-gaps, and slots. The globe solution is obtained using boundary andcontinuity conditions. It’s easy to obtain the analytical expressions of air-gap flux density, andcalculate the internal and external rotor electromagnetic torque by Maxwell stress tensor method.Compared air-gap magnetic field distributions and electromagnetic torque computed by theanalytical method with those obtained from the2-dimensional finite element method (FEM). Inaddition, it analyzes the harmonics of the air-gap magnetic field and the static characteristics ofelectromagnetic torqueSecondly, according to the magnetizing principle of Halbach arrays, it deduces themathematical model of Halbach array magnetization. An exact2-dimensional analytical methodhas also been adopted to calculate the magnetic field distribution and its torque, Analyzed andcompared the distribution of magnetic lines in the two magnetic modes, the exact analyticmethod calculation results are compared with finite element software FEMM calculated results, at the same time, it also do a comparison of air gap harmonics size and torque. The agreement ofthe results between the analytical method and FEM can lay the foundation for parameteroptimization design of magnetic gear.Thirdly, in order to enhance the magnetic gear’s torque density, it is the first time to applythe genetic algorithm optimization toolbox of Matlab(GAOT) to optimal design of magnetic gear,in the optimization process, it is no longer human intervention and it’s quicker and easier thanthe finite element method. Depending on the optimal targets, it selects some parameters for moreoptimization goals as optimization variables, and selects the appropriate operator and probability.Based upon the relationships between various parameters and static torque, the ranges of valuesfor the parameter are determined. After then, an exact analytical method is calculated theelectromagnetic torque of magnetic gear, the results are compared with the before tuning ofmagnetic gear, the better results show that the optimization algorithm is correct and valid.Finally, based on the optimum design parameters and drawings, the magnetic gear withHalbach arrays is manufactured, which ratio is-4.25:1. From the no-load test, Iron loss is themain loss of magnetic gear, and the load test is about transmission efficiency of the magneticgear when the magnetic gear drives at a fixed speed. From the experimental results, the torquedensity and transmission efficiency of prototype are very high, it has the value of promotion andapplication.Under using Halbach arrays of magnetization for a concentric magnetic gear, because ofmagnetic field mutual superposition, which makes one side of the air-gap magnetic fieldsstrength improved significantly, and can improve the torque density. At the same time, theair-gap magnetic field distribution of sinusoidal is very high and the harmonic is small. It ispossible to study on combination electrode for a low speed large torque magnetic gear. |
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