Design of a 6.8-kW Two-Phase Converter for 48V Automotive Applications

48V motor drive systems become more prevalent with the widespread introduction of low-cost micro-mobility and micro-hybrid propulsion systems. Two-phase electric machines offer a more compact and economical structure and lower cost than three-phase electric machine alternatives, while the power density and torque density remain the same. For some applications, such as 48V mild hybrid propulsion system, two-phase electric machine is a superior solution. In this paper, three topologies of two-phase voltage source inverters are compared and the three-legged configuration is selected. To obtain the optimal motor drive system cost, a 48-V silicon MOSFET-based, two-phase power converter with maximum power of 6.8kW is designed and developed. The DC-link capacitance and voltage ripple is analyzed in order to minimize the capacitor bank. The design process is explained in details and the experimental tests are included.