Analysis of Lightweight Dual-Rotor Yokeless-Stator PMSM for Electrified Aircraft Propulsion Considering Thermal Benefits of Heat Pipes

A lightweight dual-rotor yokeless-stator permanent magnet synchronous machine (PMSM) equipped with end-winding heat pipe cooling system is proposed for electrified aircraft propulsion application. The improvement in electromagnetic output performances is verified, and the critical challenge of limited surface area for axial cooling is addressed. First, the dual-rotor yokeless-stator motor topology, the end-winding heat pipe cooling method and the integrated structural configuration are designed and illustrated based on the special requirements of aircraft propulsion systems. The motor is then optimized using multi-objective genetic algorithm (MOGA). The electromagnetic performances of the dual-rotor yokeless-stator PMSM are comprehensively analyzed and compared with the conventional outer-rotor PMSM, demonstrating prominent advantages in terms of compactness, torque density, overload capability and efficiency. Furthermore, the thermal behaviors with end-winding or inslot heat pipes are comparatively investigated, with a particular focus on the influence of stack length. The results affirm that the end-winding heat pipe system can realize efficient cooling for concentrated windings, and is especially suitable for motors with compact structure. Finally, a 100-kW dual-rotor heat pipe cooled PMSM prototype is manufactured. Both electromagnetic and thermal tests validate the theoretical and simulation results.