Novel variable-mode partitioned stator switched flux memory machines for automotive traction applications

In this paper, a novel variable-mode partitioned stator switched flux memory machine (PS-SFMM) with spoke-type low coercive force (LCF) permanent magnets (PMs) is developed. Due to the changeable magnetization level and polarity of LCF PMs, the PM pole number within inner stator can be purposely varied to either 12 or 6. Thus, this pole-changing concept enables PS-SFMM to behave similarly as 12-pole conventional and 6-pole E-core SFPM machines respectively and to work within a relatively wide speed range. The flux-weakening performance can be further improved via the stepwise PM pole-changing actions. Thereafter, LCF PMs are either bi-directionally fully magnetized or non-magnetized so that the continuous accurate online PM magnetization will be less necessary, which simplifies the control effort. The machine topology and variable-mode principle are described first. The electromagnetic characteristics at different modes are then investigated individually. Finally, the global flux-weakening performance is addressed by appropriately grouping the different modes within the whole speed range, which validates the feasibility of the proposed variable-mode concept.