Influence of the radial variation of the magnet pitch in slotless permanent magnet axial flux motors

The design of slotless axial-flux machines is different from that of conventional radial-flux machines, due to their topology. In particular, the active conductors are subjected to different conditions of magnetic field along their radial length. This is enhanced in machines where the shape of the magnets is different from that of the stator poles. This paper provides a numerical approach (2D FEM) for keeping into account this configuration: the described technique allows accurate evaluation of the instantaneous torque and of the mean torque, as well as all the quantities (such as back EMF, efficiency, and so on) that characterise the machine. The algorithm is validated by means of comparisons with the experimental results from an existing machine