Powertrain modularity

Climate change has created an increased need for innovation in various sectors, including the automotive industry. Many corporations are striving to fulfil this need by developing and producing electric cars. However, the production process remains inefficient and environmentally harmful. The EU-funded HEFT project will reverse this trend by introducing a revolutionary synchronous motor for electric cars, which will be recyclable, cost-efficient and require fewer materials while producing fewer emissions and creating novel European circular economies. 

HEFT Project proposes a set of innovation challenges on electric synchronous motor configuration based on SiC inverters (direct cooling of rotor and stator, advance insulation for high voltage, multibarrier rotor topology, wave windings) and advanced materials (advanced GBD magnets, epoxy for magnet fixation, composite for motor housing, insulation resin). These innovations will result in a high-efficient and low-cost solution that will be validated on 2 motor topologies.

In this document it details the work carried out in the HEFT project with regards to the objective of improving SiC-based drive control to reduce powertrain losses and improve EV range. The following issues will be covered:
1. Online variable switching frequency control strategy to optimize drive operation and reduce inverter and motor losses.
2. Optimal flux operation point to increase motor efficiency.
3. Improved powertrain thermal management strategy.
 

All these control aspects will be used in both A+B segment motor and C+D+E segment motor, as control strategy is the same for both motors that will be designed in HEFT project (only some parameters’ tunning need to be modified). Therefore, as use case, A+B segment motor has been selected, because this motor has already been designed. However, some preliminary results regarding C+D+E segment motor are also shown in this deliverable (this motor is still under development) to show that the proposed control strategy is valid for any IPMSM.

This deliverable provides updated specifications and requirements for the electrical, electronic, and thermal management subsystems of the RHODaS powertrain, building on those previously defined. It focuses on the design of a three-level, three-phase modular T-type converter based on SiC and GaN semiconductors, which must be compact to achieve the targeted gravimetric and volumetric power densities when mounted on top of the motor. The document details the converter’s dimensions, the integration of IMD components, and the semiconductor technologies under consideration.

Because commercially available GaN devices currently support only low voltages and currents, the deliverable proposes alternative strategies, such as using prototype GaN packs or parallelising multiple transistors, alongside a roadmap to address future design challenges. It also describes the supervision and monitoring strategies, including cloud-based functions, and defines the specifications for the thermal management system, with attention to environmental conditions and cooling requirements. The report concludes with a consolidated summary of the converter specifications, providing a reference for subsequent development and validation.

This deliverable presents the design, validation, and testing of the RHODaS high‑power hybrid T‑type multilevel inverter. Chapter 2 explains the overall architecture of the inverter, including sensors, modular power stages, mechanical structure, housing, and integration. The first design of the power stage did not meet the electrical and thermal requirements; therefore, several improvements were introduced in the final stage, which are also described in this chapter. Both iterations, the initial and the final design, are documented to highlight the evolution of the system. Chapter 3 explains the initial T‑type design and the challenges encountered with the first GaN transistors, such as voltage limitations, short‑circuit behaviour, and reliability issues. Chapter 4 explains the initial inverter tests, including switching behaviour and operation at different load points, which were performed to ensure proper functionality. Finally, chapter 5 defines the comprehensive high‑power inverter tests, covering efficiency, thermal performance, and maximum power capability, with final validation to be conducted at BOSMAL’s mechanical testing laboratory. In conclusion, the deliverable documents the progression from an initial design with critical shortcomings to a robust final inverter prototype, achieving a power density of 58.6 kW/l. The initial tests confirm that the converter is both reliable and capable of operating in line with the project specifications, reaching efficiencies of up to 99%. Nevertheless, the definitive validation of the converter will be conducted at BOSMAL, where the comprehensive test procedures defined in this deliverable will be applied to ensure full compliance with the project requirements.