Comprehensive Review on Hybrid Radial-Axial Flux Permanent Magnet Synchronous Motors

This paper represents a state of art literature review for hybrid field topology electric machine. The hybrid axial/radial flux machine (HARFM) is considered a promising solution for power density enhancement of conventional machine designs used in traction applications. The HARFM integrates both axial-flux and radial-flux machine topologies in a compact space, which effectively improves the copper utilization. The HARFM rotor structure concentrates the magnetic flux into the air gap. As a result, both the induced back electromotive force and the total output power are increased. Different aspects of HARFMs presented in the literature are reviewed and analyzed. This includes machine topologies, implementation, materials and thermal analysis. The topologies are classified according to the number of rotors utilized in the motor structure. The different presented topologies demonstrate a higher output torque density compared to conventional radial and axial flux motors. The development of HARFM structure is a promising research area in the field of traction applications that can benefit from further developments in advanced designs, materials as well as detailed optimization and analysis.