Enhancing levitation force of superconductors through wavelength optimization in Halbach permanent magnet arrays

Optimizing the wavelength (gamma) of the Halbach array permanent magnet guideway (PMG) in superconducting maglev systems can improve levitation performance without consuming additional materials. The value of gamma impacts the external field intensity He and gradient backward difference He generated by the PMG. The total amount of magnetic field energy is fixed, and the gamma essentially regulates the distribution of this energy. Reducing gamma concentrates more magnetic field on the PMG surface, resulting in larger force and stiffness when the levitation height approaches zero. To validate this conclusion, experiments, approximate calculations and numerical simulations have been in all employed. However, excessive reducing gamma at higher heights is not ideal as it tends to distribute most of the field energy below the desired height. The approximate method in this paper indicates that the levitation force is positively correlated with (He22Hp-He) backward difference He . Therefore, the objective is to determine the optimal gamma that maximizes this index. Optimal values for gamma at different heights have been identified, offering guidance for PMG design. Additionally, applying these findings to two existing PMGs results in 18% and 8.6% augmentation in levitation force respectively. Furthermore, a fully optimized PMG design has the potential to achieve a levitation force of nearly 10 kN m-1, while keeping the cross-sectional areas of the PMG and SC restricted to 4450 mm2 and 2500 mm2, respectively.