Fraunhofer IISB develops 750 kW hairpin winding traction motor for hybrid-electric regional aircraft, achieving 8 kW/kg

Fraunhofer IISB has unveiled a 750 kW permanent-magnet traction motor designed for hybrid-electric regional aircraft, achieving a remarkable power density of 8 kW/kg. The motor weighs 94 kg and reaches its rated power at 65 °C coolant temperature, operating at speeds up to 21,000 rpm with a torque output of 350 Nm. This performance is enabled by advanced engineering choices, including the use of thin-lamination NO15 electrical steel, hairpin winding technology, and direct oil-spray cooling. The motor’s stator features a unique 4×3 phase hairpin winding configuration divided into four electrically independent sections, each powered by its own inverter. This arrangement enhances fault tolerance, allowing the motor to continue functioning even if one section fails. Hairpin windings also provide higher current density and improved thermal contact compared to traditional round-wire coils, while the direct oil spray cooling system effectively manages the heat generated during high-power operation. This development forms part of Project AMBER, a Clean Aviation EU initiative aiming to create a roughly 2 MW hydrogen fuel cell hybrid-electric propulsion system for regional aircraft. Fraunhofer IISB’s motor will work in parallel with Avio Aero’s Catalyst advanced turboprop engine, with GE Aerospace also contributing to the consortium. The project targets a minimum 30% reduction in CO₂ emissions compared to regional aircraft from 2020, signalling a significant step towards greener aviation. Fraunhofer IISB handled the entire motor development process, from initial concept and CAD design to manufacturing, assembly, and validation, all adhering to stringent aerospace standards. This comprehensive approach ensures the motor is optimised for the demanding requirements of hybrid-electric propulsion in aviation, marking a notable advancement in electric motor technology for sustainable flight.