General Analytical Optimization Model of Surface-Inset Electrical Machines With Even-/Odd-Segment Halbach

General analytical optimization model has been proposed for brushless surface-inset permanent magnet (PM) machines having even-/odd-segment Halbach array. The air-gap magnetic fields have been analytically obtained by solving the matrix equations of subdomain model. For the maximum air-gap magnetic field, electromotive force (EMF), and electromagnetic torque of the even-/odd-segment Halbach, the optimal pole-arc ratio of each magnet segment, and/or the optimal magnetization angle of each side-magnet have been analytically determined. Taking 16-pole/21-slot surface-inset machines with three-/four-segment Halbach magnet array as examples, the predicted results show that the globally optimized electromagnetic torques of Halbach surface-inset machine are significantly enhanced. Analytically predicted results have been validated by a finite-element (FE) technique.