Multi-objective optimization for axial field flux focusing magnetic gear with H-type modulated stator and halbach PMs arrays for wind power generation

Magnetic gears show important potential applications in the field of wind power generation equipment due to their low maintenance cost, low noise, no lubrication, and overload protection. However, the existing dual-modulated magnetic ring double modulated axial magnetic gears suffer from weak modulation effect, susceptibility to magnetic saturation, and magnetic leakage. In response to these problems, a single modulator modulated axial field flux focusing magnetic gear is proposed in this paper. This axial field flux focusing magnetic gear (AFFMG) combines an H-type modulated stator and an array of Halbach permanent magnets (PMs) and is designed to replace mechanical gearboxes in wind power generation systems. By introducing an H-type modulated stator in the middle of the high and low-speed rotor of the AFFMG, the magnetic field of the PMs is double modulated in the axial and transverse directions, and the hybrid double modulated utilization is realized. This design effectively suppresses the magnetic leakage and magnetic saturation effect of the PMs and improves the torque density and utilization rate of the PMs. In addition, the high-speed rotor PMs are magnetized with Halbach arrays, which significantly improves the magnetic flux density of the air gap and reduces the non-operating harmonics, thereby effectively improving the torque density. In this study, the topology and working principle of the proposed AFFMG are introduced in detail, and the proposed AFFMG finite element model is established. Based on the results of the comprehensive sensitivity analysis, the response surface method and the multi-objective whale optimization algorithm were used to optimize the design, and the optimal structure size parameters were determined. The performance comparison analysis verifies the effectiveness of the optimized design method. The results show that the proposed AFFMG can effectively reduce the magnetic flux leakage at the end, suppress the magnetic saturation effect, increase the torque density by 140.67%, and significantly enhance the magnetic field modulation effect. By observing the starting torque and starting speed curves, it is found that the proposed AFFMG can provide stable torque output during the start-up phase. At the same time, the torque ripple of the high-speed rotor and the external rotor is reduced by 12.31 and 16.16% respectively, and the transmission reliability is significantly improved. This study provides a useful reference for the design of high-performance new double modulated flux focusing axial magnetic gear.