Abstract
In the previous researches of hybrid magnet memory motors (HMMMs), the demagnetization characteristics of low-coercive-force (LCF) magnets have been already investigated extensively. Nevertheless, the possible irreversible demagnetization of high-coercive-force (HCF) magnets remains unexplored hitherto. In this paper, the demagnetization behaviour of HCF magnets in switched flux hybrid magnet memory machines (SF-HMMMs) accounting for the high-level current pulse is revealed and investigated. A simplified magnetic circuit model is built to illustrate when and how the DC current pulse poses the risk of irreversible demagnetization to the HCF magnets. Furthermore, the influences of temperature, DC current amplitude and HCF magnet thickness on the irreversible demagnetization effect of HCF magnets in the investigated SF-HMMM are analyzed based on finite-element (FE) analyses. The theoretical and FE results are experimentally verified by the tests on an SF-HMMM prototype.
Highlights
Memory machines (MMs)1 are of growing research interests since the magnetization state (MS) of the low-coerciveforce (LCF) magnets can be conveniently magnetized/demagnetized with a current pulse
In order to realize a convenient magnetization control, thereafter, switched flux hybrid magnet memory machines (SF-hybrid magnet memory motors (HMMMs))2,3 equipped with both high-coercive-force (HCF) and LCF magnets are proposed to achieve high-efficiency operation within a wide speed range
The parallelity between permanent magnets (PMs) and armature fields in the proposed SF-HMMMs leads to advantageous demagnetization withstand capability, the potential partial irreversible demagnetization issue is a major concern
Summary
Memory machines (MMs) are of growing research interests since the magnetization state (MS) of the low-coerciveforce (LCF) magnets can be conveniently magnetized/demagnetized with a current pulse. In order to realize a convenient magnetization control, thereafter, switched flux hybrid magnet memory machines (SF-HMMMs) equipped with both high-coercive-force (HCF) and LCF magnets are proposed to achieve high-efficiency operation within a wide speed range. The previous literatures about MMs mainly focus on the demagnetization of LCF magnets. No insight has been provided into the irreversible demagnetization behaviour of HCF magnets hitherto, especially accounting for the influence of the high-level transient current pulse on HCF magnets. The purpose of this paper is to comprehensively investigate the demagnetization characteristics of HCF magnets in SF-HMMMs
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