Design and Analysis of a Hybrid Permanent Magnet Variable-Flux Flux-Intensifying Machine

Variable flux machines utilizing low coercive-force magnet material Alnico have attracted many attentions due to its features of variable flux controllability which can obtain a wide speed range and high efficiency at the entire speed range. However, since the remnant magnetism of Alnico is always lower than rear-earth magnets, leading to a lower torque output. A hybrid permanent magnet variable-flux flux intensifying machine (HVFI-IPM) which NdFeB and Alnico are both tangential magnetized is first proposed to improve torque density. The details design of this machine is investigated and validated by finite element analysis (FEA). Besides, magnetization performance is also studied. In addition, the torque-speed envelopes and efficiency maps of different magnetization states are calculated and conclude that this machine can achieve high efficiency at the entire torque-speed range.