Electrical Resistivity and Magnetic Performance of Ceramics-Bonded Nd-Fe-B-Type Magnet Consolidated Using Dielectric Oxide Binder

Kang, Min‐Sung; Kim, K. M.; Kwon, Hansang; Kim, D. H.; Lee, J. G.; Shin, Kijung

doi:10.1109/tmag.2019.2896889

Cited by 4 publications

(3 citation statements)

References 16 publications

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“…One effective method to reduce this is increasing the electrical resistivity of magnet materials. Studies have shown that mixing high-electrical-resistivity materials with raw powders, followed by magnet fabrication, can achieve this increase for hotdeformed magnets [40,41].…”

Section: Conclusion and Future Developmentsmentioning

confidence: 99%

Development of High-Performance Hot-Deformed Neodymium–Iron–Boron Magnets without Heavy Rare-Earth Elements

Hioki

2023

Materials

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Neodymium–iron–boron magnet is an essential material for the traction motors of green vehicles because it exhibits the highest maximum energy product, (BH)max, out of all permanent-magnet materials. However, heavy rare-earth elements such as dysprosium and terbium, which are scarce resources, are added to these magnets to improve their heat resistance. To address this resource problem, considerable efforts have been made to reduce the composition of heavy rare-earth elements in these magnets without causing a significant reduction in coercivity. Hot-deformed Nd-Fe-B magnets are a category of Nd-Fe-B magnets where precious materials such as heavy rare-earth elements can be eliminated or reduced to maintain high coercivity owing to their fine microstructure. Although they are not often used for the fabrication of high-performance magnets due to their complicated production process and the difficulty in controlling their fine microstructure, after the rare-earth crisis in 2020, these magnets have begun to attract attention as a material that could increase coercivity when controlling their microstructures. This paper provides an overview of hot-deformed magnets and the efforts made to improve their properties by controlling their microstructures.

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Section: Conclusion and Future Developmentsmentioning

confidence: 99%

Development of High-Performance Hot-Deformed Neodymium–Iron–Boron Magnets without Heavy Rare-Earth Elements

Hioki

2023

Materials

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“…Marinescu et al [51] and Sawatzki et al [52] also reported the fabrication of die-upset Nd-Fe-Btype magnet with high electrical resistivity using melt-spun Nd-Fe-B-type powder doped with rare-earth salt. Kim et al [67] and Kang et al [68,69] reported remarkable enhancement of electrical resistivity in the die-upset and hot-pressed Nd-Fe-B-type magnets using an innovative technique, in which dielectric eutectic salt mixture with uniquely low melting point was doped.…”

Section: Die-upset Magnetmentioning

confidence: 99%

Prospect of developing Nd–Fe–B-type magnet with high electrical resistivity

Kwon

Kang

2019

Rare Met.

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Nd-Fe-B-type magnet is exclusively used as a rotor magnet in the traction motor of hybrid electric vehicle (HEV) and electric vehicle (EV), but its overly high operating temperature is a lingering problem attached to the magnet. The major cause of the high operating temperature is eddy current, which is readily generated in the highly conductive metallic magnet under alternating magnetic field from stator ripple. In this article, temperature rise in the Nd-Fe-B-type magnet with varying electrical resistivity under alternating magnetic field is discussed with the intention of highlighting the importance of enhancing the electrical resistivity for reducing the operating temperature of the Nd-Fe-B-type rotor magnet. Temperature rise in the Nd-Fe-B-type magnet (dielectric salt-added die-upset magnet) with high electrical resistivity is noticeably lower compared to the magnet (commercial sintered rotor magnet) with lower electrical resistivity, substantiating the theory that enhancing the electrical resistivity in the rotor magnet is fairly effective for suppressing the over-rise of its operating temperature during operation. Die-upset process is revealed to be particularly pertinent for the fabrication of highly dense salt-added magnet with high electrical resistivity.

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“…There are many ways to reduce the rotor eddy current loss, such as changing the sleeve or PM structure, but this method will reduce the output torque or PM utilization, and the strength cannot be guaranteed [6][7][8][9]. A more direct method is to reduce the electrical conductivity of PM materials, such as using other heavy metals to replace neodymium in PM materials to increase the Curie temperature of PM materials [10,11]. However, this method cannot guarantee the coercivity of PM materials.…”

Section: Introductionmentioning

confidence: 99%

Rotor electrical conductivity and eddy current loss analysis of high‐speed permanent magnet machine with a novel composite rotor

Luo

Zhang

et al. 2021

IET Electric Power Appl

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The high-temperature rise of rotor permanent magnet (PM) in high-speed PM machine (HSPMM) is one of the main bottlenecks that limits the development of HSPMM. The main reason for the increase of the PM temperature is the eddy current loss caused by highfrequency harmonics. In this study, a new type of composite magnetic material is studied, which greatly reduces the electrical conductivity of the PM and thus reduces the eddy current loss under the condition of ensuring the magnetic properties. The electrical conductivity of magnetic powder composites is calculated by introducing the improved effective medium model of the magnetic powder packing coefficient. Through the calculation of the porosity of the magnetic powder composite, the effects of the particle size, gradation and shape of the magnetic powder on the electrical conductivity of the composite were obtained. The model solves the problem of calculating the electrical conductivity of the powder structure composite rotor in eddy current loss calculation. The accuracy of the calculation is verified by the four-probe method, which provides guidance for the design of a composite rotor HSPMM.

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Electrical Resistivity and Magnetic Performance of Ceramics-Bonded Nd-Fe-B-Type Magnet Consolidated Using Dielectric Oxide Binder

Cited by 4 publications

References 16 publications

Development of High-Performance Hot-Deformed Neodymium–Iron–Boron Magnets without Heavy Rare-Earth Elements

Development of High-Performance Hot-Deformed Neodymium–Iron–Boron Magnets without Heavy Rare-Earth Elements

Prospect of developing Nd–Fe–B-type magnet with high electrical resistivity

Rotor electrical conductivity and eddy current loss analysis of high‐speed permanent magnet machine with a novel composite rotor

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