Rare Earth-Free Motors for Medium and High-Power Vehicles

With the expected surge in electric vehicle (EV) sales over the next 10 years, there is growing concern that EV manufacturing will have a major negative environmental impact and suffer from disruptions in material supply. In particular, using rare-earth metals in the permanent magnets of the most ubiquitous EV motor could become increasingly controversial. Consequently, the European Commission funded the ReFreeDrive research project (grant agreement 770143), aiming to develop next-generation electric drivetrains entirely free of rare earth raw materials. The project developed eight different rare-earth-free motor prototypes based on three major technologies: copper rotor induction motors, synchronous reluctance motors with ferrite permanent magnets, and synchronous reluctance motors without permanent magnets. Through innovations at multiple levels (rotor design, stator using hairpin windings, advanced manufacturing techniques, use of advanced materials) the project demonstrated substantial improvements compared to state-of-the-art examples of these three motor types, achieving a 30% specific torque increase, a 50% reduction in motor losses, and lowering costs by between 15% and 35%. The proposed solutions are all suitable for mass production and eliminate the risks associated with critical rare earth material supply. Through performance optimization, the alternative motors developed as part of the project close the gap to rare-earth permanent magnet motors in terms of power density and total driving efficiency for a given powertrain cost. They also have significantly less negative environmental impact compared to the reference models.