First Step to Optimum Rotor Design for E-Motors with High Power Density for Aircraft Propulsion

To meet the challenge of all-electric flight, e-motors with particularly high power density are necessary, PM synchronous machines being a preferable motor type. The rotor of an e-motor is a key factor determining its characteristics and thus also its power density. There is a wide range of rotor topologies with an even wider range of parameters to choose from. Since flux density directly affects torque generation, the idea is to determine which rotor topology achieves the best main spatial harmonic flux density to rotor weight ratio. For this purpose, a multiobjective genetic algorithm was used, which finds the best solutions in sufficient time despite the large parameter range. The evaluation of about 25000 results shows that surface mounted configurations such as traditional surface magnets or a Halbach-Array configuration provide good solutions. However, for a high torque, high current density approach, spoke-type magnets are the best, since they have advantages in terms of demagnetization. For a high-speed, low pole pair approach, V-shaped buried magnets seem to lead to the best solution. The presented approach provides a possibility to perform a pre-selection of rotor topologies, but requires more detailed application-specific investigations.