Halbach permanent magnet machines and applications: a review

Permanent magnet brushless machines employing multipole Halbach magnetised rotors are being developed for various applications, since they offer a num ber of attractive features. Alternative Halbach machine topologies are revi ewed, and the realisation of Halbach magnetised magnets from pre-magnetised sintered rare earth magnet segments (which approximate the Halbach magneti sation distribution and thereby compromise their performance), and as bonde d isotropic and anisotropic NdFeB ring magnets (which are subsequently impu lse magnetised with a Halbach field distribution), is considered. Radial- a nd axial-field, slotted and slotless, rotary and linear (tubular and planar ), and spherical Halbach magnetised brushless machines are described, and p otential applications, including a motor/generator for a high-speed fly-whe el peak power buffer, high-performance linear and rotary servo motors, and passive magnetic bearings are considered.