Magnetic field analysis and optimization of permanent magnet machines with novel two-segment Halbach array

An analytical technique for predicting and optimising the open-circuit magnetic field in brushless surface-mounted permanent magnet (PM) machines with novel two-segment Halbach array has been presented. For the maximum fundamental air-gap flux density, the optimal magnetisation angle has been analytically derived. The effect of the rotor core on the fundamental air-gap flux density in the machine has been investigated. In addition, the proposed analytical technique can also predict the induced back-electromotive force and the electromagnetic torque. The analytical results show that the electromagnetic performance can be significantly improved for the proposed two-segment Halbach array compared with the conventional two-segment Halbach array. Predicted results have been validated by the finite-element analyses for 9-slot/8-pole slotless/slotted brushless PM machines.