Design optimization of brushless synchronous machines with wound-field excitation for hybrid electric vehicles

This paper presents the design optimization and performance analyses of a wound-field type brushless synchronous machine (WF-BSM) for traction drives in hybrid electric vehicles (HEVs). Research on a WF-BSM with free rare-earth magnet becomes an attractive research topic recently due to several advantages of robust rotor structure, high power capability that suitable for high-speed motor drive system applications. Furthermore, this machine has advantages of easy cooling of all active parts in the stator. The design target is the motor with maximum power more than 60kW and maximum power density more than 2.7kW/kg. The design optimization of a WF-BSM is performed by means of a finite element analysis-based genetic algorithm (GA). As the design results, the designed machine has achieved maximum power and power density of 90.8kW and 4.11kW/kg, respectively. Thus, the designed motor enables to keep the same power density in the existing IPMSM installed on a commercial HEV.