Thrust ripple and inductances characteristics of a hybrid-excited flux-switching linear machine

Hybrid-excited flux-switching linear machine (HEFSLM) adjusts the air gap flux density by DC excitation current, which may have great influence on its performances and parameters, such as thrust force, thrust ripple, inductances and etc. This paper mainly investigates its thrust ripple and inductances characteristics under different DC excitation currents with the frozen permeability (FP) method based on finite element analysis (FEA). By the thrust ripple separation, the on-load thrust ripple is divided into three components, which stem from different causes respectively. Although the longitudinal end effect is the biggest cause, the DC current is another great factor because of the aggravated magnetic saturation level particularly under flux-weakening condition, which is totally different from traditional hybrid-excited machine. To on-load d-axis and q-axis (d-q) inductances, they also vary along with the increase of DC excitation current. Moreover, their difference is not zero and excitation level dependent, which indicating the on-load reluctance force cannot be neglected. The results are beneficial to optimization design and parameter identification of HEFSLMs.