Comparison of torque densities in alternate wound-field switched flux machines

Three types of wound-field switched flux (WFSF) machines, namely, a 24-slot/14-pole WFSF machine, a 12-slot/8-pole segmental-rotor WFSF machine and an 18-slot/10-pole WFSF machine, are compared in terms of torque density, with Toyota Prius 2010 interior permanent magnet (IPM) machine as well as the conventional switched flux PM machine in this paper. According to two-dimensional (2-D) finite element analysis (FEA), it is found that the torque density of a WFSF machine can be increased further by employing unequal slots, and it can achieve ~80% as much as that of the IPM machine under the same current density. The material costs and efficiency maps of machines are also compared in this paper.