Comparison of Halbach magnetised brushless machines having discrete magnet segments or single ring magnet

Summary form only given. Halbach magnetised brushless machines have several attractive features. Most notably, they have a sinusoidal airgap field distribution and EMF waveform, and exhibit negligible cogging torque. To date, however, Halbach magnetised machines have generally been fabricated from pre-magnetised magnet segments having appropriate magnetisation orientations, which approximates the Halbach magnetisation, and, thereby, compromises the performance. However, it is now possible to produce ring magnets with an ideal Halbach magnetisation. In this paper, for example, bonded anisotropic Halbach ring magnets, produced by orienting anisotropic NdFeB powder during the injection moulding process and subsequently impulse magnetising them with the Halbach field distribution, are considered, and the performance which results when they are employed in a brushless motor is compared with that which results when the motor is equipped with discrete magnet segments.