Research objectives The Horizon Europe projects EM-TECH and HighScape address innovative solutions for automotive electric powertrains, to achieve higher energy efficiency and reduced cost. The two projects are distinct yet complementary and synergic, as the former focuses on electric machines (e-machine), and the latter on wide bandgap (WBG) based power electronics (PE). This paper outlines the main innovations of the two projects that lead to next-generation complete powertrain solutions targeting a wide range of vehicle applications (passenger cars and commercial vehicles). EM-TECH deals with: The modular design of on-board high power density axial flux machines (AFMs) reduces the implementation cost of scalable electric axle (e-axle) powertrains; The high torque density in-wheel motors (IWMs) integrated with electric gearing expand the high efficiency region for electric corner (e-corner) powertrains; In both AFMs and IWMs, recycled magnets are used for sustainability. HighScape studies further improvement of the powertrain density, efficiency, and cost through physical and functional integration of WBG-based traction inverters, onboard chargers, DC/DC converters, and electric drives for auxiliaries and actuators. Methodology The conservativeness of sizing, rating, and rare earth materials during e-machine design will be relaxed by direct and active cooling, virtual temperature sensing, and enhanced machine control during e-machine operation. Life cycle analysis will be employed for costing evaluation and circularity of e-machines. The electric gearing is realised by reconfiguring multi-phase stator windings of IWMs for low-speed/hight-torque or high-speed/low-torque operation. Highly efficient WBG-based PE components can be physically integrated in the battery pack and IWMs to achieve zero footprint in vehicle sprung mass, enabled by using phase change materials as heat buffer and designing highly effective thermal path. The number of PE components can be reduced through functional integrations. For the drives of critical auxiliaries and chassis actuators, multi-motor inverter topologies can be designed by sharing legs and arms to reduce the count of switches and achieve the fault tolerance. Results An example of the functional PE integrations is shown in the figures below, for the IWM traction function (left subplot) and the on-board charging function (right subplot). One of the multi-phase motor traction inverters (stator windings and WBG MOSFETs) will be reused as the grid interface power factor correction (PFC) circuit where the motor stator windings act as the boost inductors. Limitation This paper focuses on the formation of innovative solutions for e-machines and PE. In the next 3 years, representative solutions will be prototyped and tested on component rigs or vehicle demonstrators, and their scalability for wider vehicle applications will be validated by hardware-in-the-loop or model-in-the-loop simulation. Authors’ other papers The authors have track record of the design and implementation of IWMs and AFMs, Si-based and WBG-based PE for vehicle applications. In this paper, innovative e-machine technologies and significant integration of PE components, which have not been published yet, enable more efficient and wider vehicle applications. Conclusion The new e-machine solutions expect high torque density (>150 Nm/litre, >50 Nm/kg) for IWMs with electric gearing, high power density (>30 kW/litre, >10 kW/kg) for AFMs, and energy loss reduction (>35% for IWMs and >25% for AFMs). The rare earth content (when considering the magnet recycle) will decrease by >30% for IWMs and >60% for AFMs. As a result, the cost is competitive (80% size reduction and >60% power loss reduction with respect to the current Si-based solutions.
Prof. Aldo Sorniotti, Professor, University of Surrey