• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.188-193
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• 2012

Permanent magnet is one of the most important parts in modern industry and the rare earth elements play an essential role for operation of permanent magnet. As is well known, the rare earth elements are mostly produced in China and the world is now facing serious problems owing to supply and demand imbalances. Many attempts have been performed to replace these rare-earth based permanent magnets by rare-earth free magnets, but they have not been successful so far. Regarding this issue, we discuss about an exchange spring magnet as a potential rare earth free permanent magnet structure.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.790-791
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• 2006

The fracture behavior and mechanical characteristics of sintered rare-earth magnets were investigated. It shows that the fracture behavior and bending strength of the magnets obviously exhibit anisotropy. Sm-Co magnets tend to cleavage fracture in the close-packed (0001) plane or in the ($10\bar{1}1$) plane. The fracture mechanism of $Nd_2Fe_{14}B$ magnet mainly appears to be intergranular fracture. The anisotropy of fracture behavior and mechanical strength of sintered rare-earth magnets is caused mainly by the strong crystal-structure anisotropy and the grain alignment texture. The effects of Nd content, and Pr, Dy substitution on the impact stability of $Nd_2Fe_{14}B$ magnets were also reported.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.137-142
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• 2021

In recent years, permanent magnets such as IPM (Interior Permanent Magnet) motors or SPM (Surface Permanent Magnet) motors that can obtain high efficiency and power density by inserting rare earth permanent magnets into the rotor are used. Research on the used electric motor is being actively conducted. Since it uses a permanent magnet, it has the advantage of high efficiency and high power density compared to reluctance motors and induction motors, but by inserting a permanent magnet into the rotor, it operates at high speeds and decreases reliability due to demagnetization of the permanent magnets, and increases the cost of rare earth metals. In this paper, in accordance with the development of future technology that can replace rare-earth permanent magnet motors and technological preoccupation of rare-earth reduction type motors and de-rare-earth motors, switched reluctance motors that do not require permanent magnets (Switched Reluvtance Motors) Motor, SRM) to drive driving control. Using the 3-phase SRM library provided by the PSIM simulation program, we will study the driving and control system modeling of SRM using the rotor position information sensor.

• Journal of the Korean Magnetics Society
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• v.21 no.6
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• pp.225-230
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• 2011

Magnetic materials has been applied to various fields due to their energy convertible properties between electrical and mechanical energy. Particularly, permanent magnets have been currently attracted much attention because they produce external magnetic field without any electrical current. For high efficiency, a demand for permanent magnets containing rare earth elements has been continuously increased, which abruptly raises the price and causes the supply difficulty of rare earth materials. Therefore, the development of permanent magnets with less or without rare earth elements become a urgent issue. In this report, the current trend and major issues on high efficiency permanent magnets, particularly exchange-coupling magnets, are discussed.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.90-90
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• 2013

Since discovery, NdFeB permanent magnet has replaced application of the conventional magnets rapidly because of its superior physical and mechanical properties. With increasing consumption of power combined with energy resource depletion, energy efficiency is becoming more and more inportant. According to recent reports, almost almost half of the electric power is consumed by motor, and NdFeB magnets which are the core component of the motor play a key role on improving energy efficiency of the devices. In parallel with finding alternatives energy resources, research works improving energy efficiecy have been conducted world wide. Althogh NdFeB magnets usage have been expanded to various applications, key materials such as Nd and Dy, resouces lean heavily on specific area, China. Magnetic industry revently experienced skyrocketing price fluctuatioin of rare earth at around 2008. Chineses government's regulations worsened the situation and arose a necessity to develop methods to minimize rare earth use. In this presentation, POSCO's recent research works on rare earth reduction is presented including novel powder alloying method using nitrate precursors. Also, future R&D plans for rare earth free magnets is briefly introduced as well.

• Journal of the Korean Magnetics Society
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• v.22 no.6
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• pp.221-227
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• 2012

High performance permanent magnets have become the subject of considerable attention because of the potential applications in the traction motors of hybrid and electric vehicles and wind generators. Nd-Fe-B magnets have attracted considerable interest due to a large maximum energy product. However, Nd-Fe-B magnet cannot be used in high temperature (${\sim}200^{\circ}C$) applications due to the thermal degradation of coercivity. Therefore, the development of high coercivity Nd-Fe-B permanent magnet is a challenging issue. In case of high coercivity Nd-Fe-B permanent magnet, an increment in the intrinsic coercivity can be easily achieved by substituting Nd atoms with Dy or Tb atoms. However, these heavy rare-earth elements are known to cause a decrease in remanence due to the antiferromagnetic coupling between Dy and Fe atoms. In addition, Dy is relatively expensive and being limited in quantity. Hence, a new technology that can increase the coercivity of Nd-Fe-B sintered magnet using only a small amount, or even, no amount of heavy rare-earth elements is being investigated. This article describes the research trend in reducing the heavy rare-earth elements in Nd-Fe-B magnets.

• Journal of Powder Materials
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• v.26 no.2
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• pp.146-155
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• 2019

Rare earth magnets are the strongest type of permanent magnets and are integral to the high tech industry, particularly in clean energies, such as electric vehicle motors and wind turbine generators. However, the cost of rare earth materials and the imbalance in supply and demand still remain big problems to solve for permanent magnet related industries. Thus, a magnet with abundant elements and moderate magnetic performance is required to replace rare-earth magnets. Recently, $a^{{\prime}{\prime}}-Fe_{16}N_2$ has attracted considerable attention as a promising candidate for next-generation non-rare-earth permanent magnets due to its gigantic magnetization (3.23 T). Also, metastable $a^{{\prime}{\prime}}-Fe_{16}N_2$ exhibits high tetragonality (c/a = 1.1) by interstitial introduction of N atoms, leading to a high magnetocrystalline anisotropy constant ($K_1=1.0MJ/m^3$). In addition, Fe has a large amount of reserves on the Earth compared to other magnetic materials, leading to low cost of raw materials and manufacturing for industrial production. In this paper, we review the synthetic methods of metastable $a^{{\prime}{\prime}}-Fe_{16}N_2$ with film, powder and bulk form and discuss the approaches to enhance magnetocrystalline anisotropy of $a^{{\prime}{\prime}}-Fe_{16}N_2$. Future research prospects are also offered with patent trends observed thus far.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.89-89
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• 2013

Rare earth (RE) - transition metal based high energy density magnets are of immense significance in various engineering applications. $Nd_2Fe_{14}B$ magnets possess the highest energy product and are widely used in whole industries. Simultaneously, composite alloys that are cheap, cost effective and strong commercially available have drawn great attention, because rare-earth metals are costly, less abundant and strategic shortage. We designed rare-earth free alloys and fabrication process and developed novel route to prepare $Nd_2Fe_{14}B$ powders by wet process employing spray drying and reduction-diffusion (R-D) without the use of high purity metals as raw material. MnAl-base permanent magnetic powders are potentially important material for rare-earth free magnets. We have prepared the nano-sized MnAl powders by plasma arc discharge and micron-sized MnAl powders by gas atomization. They showed good magnetic property, compared with that from conventional processes. $Nd_2Fe_{14}B$ powders with high coercivity of more than 10 kOe were successfully synthesized by adjusting R-D step, followed by precise washing system. It is considered that this process can be applied for the recycling of RE-elements extracted from ewaste including motors.

• Journal of Magnetics
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• v.1 no.2
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• pp.94-100
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• 1996

A hysteresis loop tracer using a pulsed high magnetic field of 113.4 kOe, which is suitable for rare earth based permanent magnets, is constructed. The high pulsed magnetic field is generated by discharging a large capacitance charge (5 mF) with a voltage of 600 V into an air solenoid with the inner diameter of 14 mm, outer diameter of 36 mm and the lingth of 34 mm. A computer simulation method is used for the construction of an electromagnet to optimize the many parameters such as the discharge current, generated pulsed magnetic field intensity, thermal dissipation, capacitance, charged voltage, period of damping oscillation and solenoid geometry. By using the hysteresis loop tracer constructed in this work, we are able to measure hystersis loops of several rare earth based permanent magnets with large values of the remanent magnetization, coercvity and energy product.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.620-625
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• 2013

This paper presents the design of a switched reluctance motor (SRM) for electric air conditioning compressors which are applied to hybrid electric vehicles (EVs). The motor for driving air conditioning compressor which is recently used on EV(electric vehicle) / HEV (hybrid electric vehicle) is PMSM(permanent magnet synchronous motor) or BLDCM(brushless DC motor). However disadvantage of motors that uses permanent magnets are vulnerable to high temperatures because of the demagnetization by the high temperature and the permanent magnet is expensive because of the high price of rare earth materials from China's monopoly. Therefore, in the automotive insustry is interested in the non-rare-earth motors. SRM has many advantages. it's resistant to high temperatures, price is cheaper, because there are no permanent magnets and winding in the rotor. Also it's high relability and efficiency, suitable for high-speed operation because of structure is simple. In this paper, the SRM, non-rare-earth motor, are designed, analyzed and experimented drive to replace an existing electric compressor drive motor.