Steady-state Analysis of Cycloidal Magnetic Gear Based on Equivalent Motion Modes

Cycloidal Magnetic Gear (CMG) has the advantages of high torque density, high transmission ratio, and steady-state performances are vital for its future industrial applications. CMG has two operation modes with high transmission ratio, namely, reducer mode and windlass mode, and the inner rotor needs to perform curve translation under both working modes. However, the existing commercial finite element software cannot set this complex motion form when using transient field simulator (TFS), which makes it difficult to obtain the steady-state electromagnetic characteristics of CMG in the design stage. This paper proposed a CMG steady-state electromagnetic performance analysis method based on equivalent motion modes (EMMs). Firstly, the operation modes of CMG with high transmission ratio is demonstrated. Then, the general mode is proposed, and the EMMs are derived through kinematic analysis of original two modes and general mode. Next, by using magnetostatic field simulator (MFS), the input and output torques also satisfy the transmission ratio, which verifies the correctness of the EMMs. Finally, based on EMMs, the magnetic field distributions under no-load and full-load show that the CMG pole coupling rate reaches 94%; through flux density FFT analysis, the modulation effect of non-uniform air gap is demonstrated. In addition, the steady-state torques simulation results show that the torque fluctuation is less than 2%. At last, the steady-state eddy current loss is calculated, it is found that the eddy current loss is independent of the load and proportional to the square of the output speed ω
1
.