Electromagnetic performance analysis of coaxial magnetic gear with three rotors featuring a monotonic magnetic ring and dual modulation enhancement effect

The strength of magnetic field modulation effect of coaxial magnetic gears is a key factor to measure the transmission performance of coaxial magnetic gears. Although the dual modulation coaxial magnetic gears with double modulating magnetic rings can effectively enhance the magnetic field modulation effect, there are still the problems of low torque density and serious magnetic leakage loss. In order to address the above problems, this paper proposes a three-rotor single-regulating ring dual-modulated coaxial magnetic gear that simultaneously adopts the “sum modulation effect” and “differential modulation effect”, and analyzes its working principle and the structure of multiple magnetic circuits that inhibit magnetic saturation; establishes the corresponding finite element model and analyzes its electromagnetic performance. The finite element model is established and its electromagnetic performance is simulated and analyzed; the results show that the modulation effect of the single-regulating magnetic ring double-modulated coaxial magnetic gear is strong, but the steady-state torque fluctuation of the outer rotor is large. To address this problem, Halbach magnetization is used to suppress the large fluctuations in the torque of the outer rotor, and the torque fluctuation of the outer rotor is reduced by 5.67% after the improvement. The single-modulating magnetic ring dual modulation coaxial three-rotor magnetic gear proposed in this paper enhances the magnetic field modulation effect while suppressing the magnetic saturation phenomenon, improves the utilization rate of permanent magnets, reduces the amount of modulating ring, and provides a reference for the research of single-modulating magnetic ring dual modulation coaxial magnetic gear.