Investigation of Torque Contributions of Main-order Working Harmonics in Consequent-pole PM Vernier Machines

In this paper, the torque contributions of the main-order working harmonics in consequent-pole permanent magnet (CPM) Vernier machines are investigated and quantified to provide an in-depth understanding of their torque production mechanism. Two typical CPM Vernier machines with regular and split-teeth structures are selected and comparatively studied with conventional CPM machine. Due to the unipolar PM magneto-motive force (MMF) distribution and double-side slotting effect, the CPM designs exhibit various air-gap permeance components and resultant multiple air-gap field harmonics for torque generation. The torque contributions of the main-order working harmonics are identified and quantified by Maxwell stress tensor (MST) method. Moreover, the influence of the torque proportions of the three CPM machines with different gear ratios are subsequently investigated. Besides, the torque contributions of the corresponding surfaced-mounted PM (SPM) counterparts are also studied to present a comparison of their difference.