Torque Harmonics Mitigation in Wound Field Synchronous Generators With Asymmetric Rotors for More Electric Aircraft

As more electric aircraft (MEA) platforms emerge, wound field synchronous generators (WFSGs) are gaining renewed attention due to their high reliability and costeffectiveness, particularly from the elimination of rare-earth permanent magnets. However, WFSGs pose unique design challenges, notably the presence of high-order torque harmonics and induced voltage harmonics in the windings, which contribute to acoustic noise and mechanical vibration, which are critical issues in MEA applications. This paper proposes an asymmetric rotor design strategy to suppress torque harmonics by intentionally shifting the magnetic flux distribution. Since torque harmonics originate from the interaction between stator and rotor magnetomotive forces and slot harmonics, their phase and magnitude can be modulated through rotor asymmetry. Finite element analysis is used to evaluate torque harmonic behavior and to design an optimal asymmetric rotor geometry for harmonic cancellation. The proposed design is benchmarked against a conventional symmetric rotor and other torque ripple mitigation approaches. Simulation results demonstrate that the dominant torque harmonic and overall torque ripple are reduced by approximately 94 % and 75.7 %, respectively. Moreover, the proposed design maintains torque performance comparable to that of existing ripple reduction techniques while providing enhanced manufacturability, offering a promising solution for next-generation WFSGs in electric aviation.