Abstract
Aiming at extending the operating speed range and increasing the machine efficiency, three series-configuration hybrid-permanent-magnet variable-flux machines (HPM-VFMs) with both low and high coercive-force magnets are proposed. The magnetization characteristics of the machine with different dimensions of the high coercive-force (HCF) magnet are investigated. Then, in order to improve the contribution rate of the HCF magnet, two improved topologies are presented. The electromagnetic characteristics of the two proposed machines, including back electromotive force (EMF), maximum torque characteristics, magnetization state (MS) variation range and magnetic field distribution, are comprehensively analyzed and compared. The influence of different types of windings on the performance of the machine is also investigated. Finally, the torque-speed curves of the machine under different MSs are given by finite element method (FEM). The results show that the HPM-VFM can operate over a wide-speed range with high efficiency.
Highlights
The unadjustable air-gap flux of the conventional rare-earth PM machine leads to limited constant-power speed range (CPSR), and the efficiency is lower at high speed region which results from the inescapable flux-weakening current
Since the low coercive-force (LCF) magnet is utilized in the variable-flux PMSM (VF-PMSM), the air-gap flux can be changed by applying d-axis current pulse to re/demagnetize the LCF magnet
When the NdFeB is in both d and q axes, the Lq of the machine can be further decreased, and higher positive d-axis current can be applied under load condition
Summary
Permanent-magnet (PM) synchronous machines (PMSMs) are widely used in servo systems, traction fields and household applications owing to their high power density and high efficiency. the unadjustable air-gap flux of the conventional rare-earth PM machine leads to limited constant-power speed range (CPSR), and the efficiency is lower at high speed region which results from the inescapable flux-weakening current.. The unadjustable air-gap flux of the conventional rare-earth PM machine leads to limited constant-power speed range (CPSR), and the efficiency is lower at high speed region which results from the inescapable flux-weakening current.. The unadjustable air-gap flux of the conventional rare-earth PM machine leads to limited constant-power speed range (CPSR), and the efficiency is lower at high speed region which results from the inescapable flux-weakening current.2 To improve this situation, the concept of variable-flux PMSM (VF-PMSM) is proposed.. Since the low coercive-force (LCF) magnet is utilized in the VF-PMSM, the air-gap flux can be changed by applying d-axis current pulse to re/demagnetize the LCF magnet. For parallel-configuration HPM-VFMs, wide range of flux regulation capability can be realized, because the magnetization orientation of LCF magnets can be changed in two directions..
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