Research And Optimization Of Halbach Array Based On Equivalent Magnetic Circuit Network Method

Cylindrical dipolar Halbach array with ideal magnetization can generate a perfect uniform magnetic field within the cavity side, whose magnetic flux density only affected by the ratio of inner and outer diameter. This particular structure of permanent magnet has small external magnetic leakage and an iron yoke is needless. The structure has great potential because it increases the utilization of permanent magnet material, also reduces the size and weight of the instrument.Restricted by the technics and properties of permanent magnet, Halbach array of practical application always be a combination of a certain number of unit magnets. By comparing the two-dimensional field solution of ideal and actual discrete dipolar Halbach array, it can obtain that what caused the magnetic flux density distribution appearing uneven at the edges is discrete approximation of the magnetization direction, without considering the change of relevant geometric parameters and magnetic properties.To further discuss the impact of magnetic parameters and to find the corresponding optimal strategy, the paper used a modeling method——equivalent magnetic circuit network method, which is a combination of numerical and analytical solution, to deal with the simulation and analysis of a dipolar Halbach array. The results of magnetic flux density distribution and variation on X-axis are corresponding with the two-dimensional field solution. Without changing the number of unit magnets, the paper proposes a new form of magnetization direction which is closer to the ideal linear distribution. This improved magnetization mode can be achieved with a layered structure. Comparing with a dipolar Halbach magnet array based on sector unit magnets, whether the equivalent magnetic circuit network simulation results or the two-dimensional field solution of the optimized array are verified with the conclusions that crescent unit magnets can effectively increase the field homogeneity within the array.In the two-dimensional field solution of crescent-shaped Halbach arrays, both the magnetic flux density at origin and the amplitude of first harmonic can be simulated by finite element method to verify there relationship with the shape of magnets. The conclusions fully proved the dual character of angleα, which is that an increased level of harmonic suppression associated with a decreased magnetic flux density in central area to some extent. The compromising structure with isosceles right triangle can ensure a strong field based on lower harmonic amplitude. In addition, this structure has greatly improved the utilization of rough material and reduced the difficulty of cutting. This new type of dipolar Halbach array is suitable for engineering applications.