Abstract
In this paper, the magnet eddy current characteristics of a newly developed variable flux memory machine (VFMM) is investigated. Firstly, the machine structure, non-linear hysteresis characteristics and eddy current modeling of low coercive force magnet are described, respectively. Besides, the PM eddy current behaviors when applying the demagnetizing current pulses are unveiled and investigated. The mismatch of the required demagnetization currents between the cases with or without considering the magnet eddy current is identified. In addition, the influences of the magnet eddy current on the demagnetization effect of VFMM are analyzed. Finally, a prototype is manufactured and tested to verify the theoretical analyses.
Highlights
Variable flux memory machines (VFMM) equipped with low coercive force (LCF) aluminumnickel-cobalt (AlNiCo) magnets[1,2,3,4] are recognized as a viable candidate for wide-speed-range applications
VFMMs usually employ AlNiCo permanent magnets (PM), of which electric conductivity PM is much higher than neodymium-iron-boron (NdFeB) commonly used in the conventional PM machines.[4]
Where Je and ν are the magnet eddy current density of AlNiCo PM, respectively; σ is the electrical conductivity of AlNiCo PM, which is approximately 1.6×106 S/m; A is the vector magnetic potential, M is the magnetizing intensity, J0 is the current density
Summary
Variable flux memory machines (VFMM) equipped with low coercive force (LCF) aluminumnickel-cobalt (AlNiCo) magnets[1,2,3,4] are recognized as a viable candidate for wide-speed-range applications. The armature windings can energize a temporary d-axis magnetizing current pulse to enable online flux control with negligible excitation copper loss. VFMMs usually employ AlNiCo PM, of which electric conductivity PM is much higher than neodymium-iron-boron (NdFeB) commonly used in the conventional PM machines.[4] the magnet eddy current analyses in VFMM remains unreported in existing literature. The influence of the PM eddy current on the magnetization characteristics of VFMM is unveiled and analyzed. The triangle air-gap flux barriers are inset between two adjacent NdFeB PM segments to alleviate the armature demagnetization effect on AlNiCo PMs. along AMB and stabilize at B as a new operating point. The air-gap flux of the proposed VFMM can be flexibly adjusted by changing magnetizing state of AlNiCo PMs online.
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