Comparative Study of Biased Flux Permanent Magnet Machines with Doubly Salient Permanent Magnet Machines Considering with Influence of Flux Focusing

X. Liu, J. T. Shi, Z. Q. Zhu, D. Wu

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Different from the doubly salient permanent magnet (PM) machines (DSPMMs), the stator/rotor pole number combination (Ns/Nr) in biased flux PM machines (BFPMMs) is flexible and Nr can be any integer except the phase number and its multiples. When Ns/Nr 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 Ns/Nr 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 Ns/Nr BFPMM exhibits about 18% higher average torque and 80% lower torque ripple than the optimized 6/4 Ns/Nr 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.

Original languageEnglish
Pages (from-to)281-289
Number of pages9
JournalElectric Power Systems Research
Early online date20 Aug 2016
Publication statusPublished - 1 Dec 2016
Externally publishedYes


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