A compact 110 kVA, 140°C ambient, 105°C liquid cooled, all-SiC inverter for electric vehicle traction drives

Wide bandgap materials are having a transformational impact on the electrical, thermal, and mechanical performance of military, industrial, and commercial power electronic systems where silicon (Si) power semiconductors are the present material technology of choice. This paper reports on the design, analysis, and experimental verification of a compact allsilicon carbide (SiC)-based inverter to meet the inhospitable environmental demands of hybrid, plug-in hybrid, extended-range electrified vehicles, and fuel cell vehicle architectures. The compact 4.8 L, 6.6 kg inverter achieves a volumetric and gravimetric power density of 23.1 kVA/L and 16.8 kVA/kg, respectively. Three 1200 V, 3.6 mΩ, half-bridge power modules, each containing seven 25 mΩ SiC MOSFETs and six 50 A Schottky barrier diodes (SBDs) per switch position, comprise the power stage. Significant improvement in conduction, switching, and reverse-recovery losses allowed this SiC MOSFET-based inverter to achieve 96.3% average efficiency and 98.9% average peak efficiency over all experiments. This is superior to Si IGBT-based inverters throughout the entire range of torques, speeds, and bus voltages — and especially at light load operating points typical of electric vehicles. Dynamometer experiments used a 20 kHz switching frequency, double-update space-vector modulation, thermal controls for ambient and coolant temperatures, custom data acquisition, and a commercial three-phase power meter to collect performance data over 500 to 6000 RPM, 5 to 180 N-m, four bus voltages, and six thermal cases.