1.2 kV Heavy-Duty Electric Vehicle Powertrains: System-Level Analysis and Holistic Efficiency Optimization of the Traction Inverter

The electrification of heavy-duty vehicles (HDVs) demands drivetrain architectures capable of supporting multi-hundred-kilowatt continuous operation and megawatt-level fast charging. Conventional 400–800 V powertrains are increasingly constrained by high currents, cable losses, and thermal stress. Recent developments in high-voltage silicon-carbide (SiC) power modules and the Megawatt Charging System (MCS) standard have opened the door to 1200 V dc-link architectures for next-generation HDVs. This work presents a comprehensive system-level assessment of increasing the dc-link voltage from 800 V to 1200 V, covering implications for the battery pack, traction inverter, and electric machine. A unified virtual-prototyping and experimental-validation workflow is developed to evaluate inverter conduction and switching losses, thermal behaviour, and volume trade-offs. A holistic inverter optimization is then performed to determine the efficiency-optimal switching frequency, accounting simultaneously for semiconductor losses and motor harmonic losses. Experimental results from a 250 kW, 1.2 kV SiC-based traction inverter prototype validate the analytical loss model. The findings show that raising the dc-link to 1200 V enables cable-mass reduction and compatibility with MCS standard, while preserving >99% measured efficiency.