Performance and design optimisation of electric motors with heteropolar surface magnets and homopolar windings

Abstract

Electric motors that embody heteropolar arrays of rotor magnets interacting with homopolar stator windings are capable of exceptionally high levels of torque per unit volume or mass. Design studies of the surface-magnet form of this class of machine have determined optimum values for the following ratios: C-core pitch/gap, magnet depth/gap, and C-core width/C-core pitch. The results are presented partly in the paper, which concentrates on three-dimensional computational design studies and on physical discussion of behaviour, and partly in a companion paper, which concentrates on theory of performance and figures of merit for design.