Comparison of alternative topologies for VRPM (transverse-flux) electrical machines

This paper is concerned with a comparison of relative advantages and disadvantages of three alternative topologies for the general class of electric motors in which stator windings excite an air gap magnetic field of one pole-number, which is then modulated by a toothed steel structure so as to enable interaction with a heteropolar field of different pole-number produced by an arrangement of rotor permanent magnets. Such machines are variously described as variable-reluctance permanent-magnet (VRPM) or transverse-flux. The tree alternative topologies considered are: single-sided surface-magnet, single-sided surface magnet with stator bridges, and double-sided flux-concentrated.