Comparative study of biased flux permanent magnet machines with doubly salient permanent magnet machines considering with influence of flux focusing

摘要

Different from the doubly salient permanent magnet (PM) machines (DSPMMs), the stator/rotor pole number combination (N-s/N-r) in biased flux PM machines (BFPMMs) is flexible and N-r can be any integer except the phase number and its multiples. When N-s/N-r differ by one, 6-stator pole BFPMM exhibits bipolar phase flux-linkage and symmetrical phase back-electromotive force waveforms. Based on the optimal 6/7 N-s/N-r and the rated copper loss, the torque density of BFPMMs is enhanced by 19%, 18.8% and 40.3% respectively when employing the flux-focusing structures with inner-type, outer-type and combined-type. Meanwhile, the PM utilization efficiency is also enhanced. Moreover, based on the inner type flux-focusing structure, the optimized 6/7 N-s/N-r BFPMM exhibits about 18% higher average torque and 80% lower torque ripple than the optimized 6/4 N-s/N-r DSPMM. Further, the unbalance between phases which is observed in DSPMMs is overcome in the BFPMMs. The analyses are validated experimentally on a prototype machine. (C) 2016 Elsevier B.V. All rights reserved.