Design investigation of hybrid excitation flux switching machine for high-speed electric vehicles

Permanent magnet (PM) and field excitation coil (FEC) in Hybrid Excitation machine (HEMs) act as a main flux sources which has numerous attractive features compared to interior permanent magnet synchronous machines (IPMSM) usually employed in hybrid electric vehicles (HEVs). The advantage of both permanent magnet and field excitation coil located on the stator is robust rotor structure alike with switch reluctance machine (SRM). Furthermore, this machine becoming more attractive because of variable flux control capabilities from FEC, which is appropriate to be applied for high-speed motor drive systems. This HEM can be categorized as hybrid excitation flux switching machine (HEFSM). In this paper, a novel 12Slot-10Pole HEFSM in which the FEC is wounded in radial direction on the stator is proposed for traction drives in HEVs. The design target of maximum torque and power are 303Nm and 123kW, respectively. Moreover, maximum power density of more than 3.5kW/kg is to be achieved, resulting that proposed motor have better power density compared to existing IPMSM. Deterministic design optimization technique based on 2D-FEA is used to treat design parameters defined in rotor, armature coil slot and FEC slot until the target performances are achieved, under maximum current density condition for both armature coil and FEC. The final results prove that the final design HEFSM is able to keep the equivalent torque density in existing IPMSM installed on commercial HEV.