Design of a Multiphase Hybrid Permanent Magnet Generator for Series Hybrid EV

Design of a multiphase hybrid permanent magnet (HPM) generator for series hybrid electric vehicle (SHEV) application is presented in this paper. The proposed hybrid excitation topology together with an integral passive rectifier replaces the permanent magnet (PM) machine and active power electronics converter in hybrid/electric vehicles, facilitating the control over constant PM flux-linkage. The HPM topology includes two rotor elements: a PM and a wound field (WF) rotor with a 30% split ratio, coupled on the same shaft in one machine housing. Both rotors share a nine-phase stator that results in higher output voltage and power density when compared to three-phase design. The HPM generator design is based on a 3-kW benchmark PM machine to ensure the feasibility and validity of design tools and procedures. The WF rotor is designed to realize the same pole shape and number as in the PM section and to obtain the same flux-density in the air-gap while minimizing the WF input energy. Having designed and analyzed the machine using equivalent magnetic circuit and finite element analysis, a laboratory prototype HPM generator is built and tested with the measurements compared to predicted results confirming the designed characteristics and machine performance. The paper also presents comprehensive machine loss and mass audits.