Performance Comparison of Surface-Inset Machines With Two Layer Equal/Unequal Magnet-Arc Halbach Magnets

The electromagnetic performances of surface-inset machines with two layer equal/unequal magnet-arc Halbach magnets are compared. The magnetic field distribution is analytically obtained by analyzing the outer/inner layer Halbach magnets separately. Through presented analytical technique, the magnetization angles of each layer Halbach magnets are analytically optimized. Considering the practical application of relatively large usage of magnets, the larger the outer layer magnet-arc ratio, the better the performances. The analytical predictions show that the optimal two layer unequal magnet-arc Halbach machine has a much higher sine degree of both the airgap flux density and the back-electromotive force and a much lower torque ripple than the optimal two layer equal magnet-arc Halbach machine. The finite element analysis and analytical prediction results are compared.