Permanent magnet bearing design: optimising the magnetisation direction

Permanent magnet bearings may be conveniently employed in several mechanical applications when friction and wear have to be avoided. The mechanical behaviour of these components is defined by the force acting between the elements of the bearing and by the stiffness of the system. In order to get the desired performance of the bearing a compromise of force and stiffness can be achieved, e.g. by selecting the magnetisation direction of the elements. The paper reviews some general criteria for permanent magnet bearing design and proposes a method for evaluating the most suitable magnetisation direction, based on the equivalent current method and employing Finite Element analyses. Three sample cases of annular and tapered bearing are reported, for which design maps for axial and radial bearings are also presented