HighScape - Report on family of WBG-based integrated traction inverters with dynamically reconfigurable windings and innovative cooling solutions (D3.3)

This report, part of the Horizon Europe-funded HighScape project, presents a comprehensive study on innovative traction inverter systems for electric vehicles (EVs) based on wide bandgap (WBG) semiconductors. The focus is on dynamically reconfigurable windings and integrated on-board charging (IOC) solutions, aiming to enhance efficiency, scalability, power density, and cost-effectiveness in next-generation EV drivetrain architectures.

The core innovation centers around e-gears, which are reconfigurable winding systems that extend the operating range of electric traction machines by dynamically altering the winding topology between series and parallel configurations. Two main implementations are explored: one using mechanical relays and the other based on semiconductor tap-changer circuits.

The mechanical relay-based e-gear offers a cost-effective and efficient solution, enabling a switch between high-torque (series) and high-speed (parallel) modes. An extension of the speed range from 1000 to 2000 rpm with minimal efficiency loss (only 0.09% reduction compared to baseline), and a reconfiguration time under 35 ms, comparable to high-end automotive gearboxes were achieved.

The semiconductor-based e-gear employs a more sophisticated architecture using SiC MOSFETs and diode rectifiers. It enables faster switching (<10 ms) and avoids torque interruption during transitions. However, this comes at the cost of increased complexity and reduced efficiency (average drop of 3.46%) due to additional conduction and switching losses.

Additionally, the report investigates both single-phase and three-phase integrated on-board chargers, leveraging the same motor windings to provide bidirectional charging functionality. Multiple configurations are analyzed, including boost PFC, interleaved PFC, and hybrid topologies. The designs aim to reduce component count, improve power factor, and eliminate the need for access to the motor’s star point, making them viable for single-motor EV platforms.

Simulation and experimental results confirm the feasibility of the proposed designs, highlighting the trade-offs between system complexity, efficiency, torque capability, and reconfiguration speed. Overall, the HighScape e-gear and IOC technologies provide a promising pathway for more compact, versatile, and efficient EV drivetrain systems.