Based on the effects of magnetization of permanent magnet(PM) on the magnetic field distribution, an analytical method was presented to solve the slotted air-gap of a surface PM contra-rotating motor(CRM) with three common types of magnetization field patterns, Radial, Parallel and Halbach magnetization. This analytical method is very effective for forecasting the magnetic field distribution and in agreement with the results of finite-element simulations. According to the analysis of the differences between the fields of the machine with different magnetizations, the accurate 2D finite-element analysis model was established in both internal and external rotor CRM. The testing and simulation results showed that the external rotor CRM with radial magnetization has a greater flux density and trapezoidal wave which is suitable for brushless DC motor, and the internal rotor CRM with parallel magnetization can improve the sinusoidal waveform distribution and has a greater flux density. The air-gap flux density of Halbach magnet motor has the most sinusoidal waveform distribution which demonstrates that Halbach magnet is suitable for multi-polar PM motor.
