Cross coupling effect in hybrid magnet memory motor

Memory motor has been researched extensively in the last decade due to its online magnetization capability. Among many types of designs, hybrid magnet memory motor (HMMM) has highest torque density. This paper investigates the cross coupling effect of HMMM in the motor topology proposed by Sakai. The analysis model is introduced firstly. Based on the magnetic circuit model, the mechanism of opencircuit cross coupling effect is investigated while the ideal condition for eliminating this effect is proposed. Later, the on-load cross coupling effect is also analysed by both magnetic circuit model and 2D FEA focusing on coercive force (Hc) of magnet and interaction between two types of magnets as well as magnetic saturation. Meanwhile, the magnetization characteristics are calculated as well. The results show that increasing Hc of low coercive force (LCF) magnet can reduce the cross coupling effect but increase the difficulty of online magnetization. Therefore, a trade-off exists for choosing proper LCF magnet in HMMM.