Curvature Effects in Radial-Field Permanent Magnet Machines

The paper describes two analytical models for predicting the magnet/airgap flux density distribution in radial-field machines having permanent magnets mounted adjacent to the airgap. The models differ in that inter-pole leakage is neglected in the first and accounted for in the second. However, amongst other things, both allow the determination of the spread of magnet working points due to flux focusing. Furthermore, it is shown that for machines in which the magnets are mounted on an inner hub an optimal magnet thickness exists for which the magnetic loading in the airgap is a maximum.