• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1043-1044
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• 2011

This paper discusses the electromagnetic and mechanical design considerations to improve the design accuracy and power to mass ratio of multi-stack axial flux permanent magnet synchronous generator (AFPMSG). Design accuracy of multi-stack AFPMSG for direct drive wind turbine application is improved by considering magnetic flux leakages and fringing effect. FEM structural analysis is utilized to increase power to mass ratio of three-stack AFPMSG by reducing the rotor yoke thickness considering magnetic and centrifugal forces and Von Mises stress distribution.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1007-1008
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• 2011

LSPM(Line Start Permanent Motor)은 기존의 가정용으로 널리 사용되고 있는 단상유도기에 영구 자석을 삽입함으로써 별도의 회로 없이 정상상태에서 동기기로 작용하는 고효율의 전동기이다. 하지만 기동시 높은 전류로 인한 전기자 반작용과 온도 상승으로 인하여 자석의 불가역 감자가 빈번하게 일어나는 문제점을 가지고 있다. 이에 본 논문은 모터 형상에 따른 영구자석의 퍼미언스 계산을 통해 동작점을 산정함으로서 불가역 감자가 발생하지 않는 영구자석의 최적의 사이즈를 선정하는데 목적을 두었다.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.754-756
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• 2001

This study investigates the characteristics of touch-free permanent magnet gear according to design parameters. The effects of the design parameters on the magnetic torque is analyzed by using 3 dimensional Finite Element Method (FEM). The considered parameters are magnetization thickness, skew angle, stack length, inner and outer diameter and the number of pole. And the validity of analysis method is confirmed by the experimental results.

• New & Renewable Energy
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• v.2 no.3
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• pp.10-14
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• 2006

We have designed and fabricated coil structures by gold electroplating technique. The thickness, width, and length are $7{\mu}m,\;20{\mu}m$, and 1.6m, respectively. With vibrating a magnet on the surface of a fabricated electroplated coil, the micro power generator produce an alternating voltage. We have changed the vibrational frequency from 0.5Hz to 8Hz. The generated voltage was 106mV at 3Hz and 198mV at 6Hz. We have rectified and stepped up the input voltage using a quadrupler circuit. After using the step up circuit, the measured voltage was 81mV at 3Hz and 235mV at 6Hz.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.110-112
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• 2004

The magnetization directions of a polar anisotropic ferrite-bonded magnet are analyzed by finite element method (FEM). The influence of the width of Sm-Co magnets for magnetic field generation is investigated. The surface flux densities of the polar anisotropic magnets are analyzed and compared according to the pole number and thickness of the magnets. And the electromotive force (EMF) values of brushless DC motors with the magnets are investigated.

• Journal of Powder Materials
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• v.20 no.3
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• pp.169-173
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• 2013

High-coercive (Nd,Dy)-Fe-B magnets were fabricated via dysprosium coating on Nd-Fe-B powder. The sputtering coating process of Nd-Fe-B powder yielded samples with densities greater than 98%. $(Nd,Dy)_2Fe_{14}B$ phases may have effectively penetrated into the boundaries between neighboring $Nd_2Fe_{14}B$ grains during the sputtering coating process, thereby forming a $(Nd,Dy)_2Fe_{14}B$ phase at the grain boundary. The maximum thickness of the Dy shell was approximately 70 nm. The maximum coercivity of the Dy sputter coated samples(sintered samples) increased from 1162.42 to 2020.70 kA/m. The microstructures of the $(Nd,Dy)_2Fe_{14}B$ phases were effectively controlled, resulting in improved magnetic properties. The increase in coercivity of the Nd-Fe-B sintered magnet is discussed from a microstructural point of view.

• Journal of Navigation and Port Research
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• v.29 no.2
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• pp.147-150
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• 2005

We suggest a cast Alnico magnet as a new microwave absorber. The proposed Alnico microwave absorber shows advanced microwave absorption properties of 24 dB at 13.3 GHz for the thicknesses of 1 mm We also investigated the effects of the carbon, which qjfects strongly to microwave absorption in Alnico magnet microwave absorbers. Central frequency shifts toward lower frequency with increasing Alnico content which is related to the frequency to show tan 8 > 1. Also, we investigated the sample thickness dependence on the microwave absorption properties.

• Journal of Magnetics
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• v.8 no.4
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• pp.157-159
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• 2003

The strengths of the inter-grain exchange interaction were evaluated for nanocrystalline $Nd_{2.33}Fe_{14}B_{1.06}Si_{0.21}$ magnets of different grain size by comparing the $_{i}H_{c}$ calculated by micromagnetics with the experiments. With increase of the grain boundary thickness to that of the magnet of grain diameter 12.4, 24.8, 37.2 and 49.6 nm, the strengh of the interaction in reference to that without the grain boundary phase decreases to 83％, 69％, 54％ and 42％.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.3 s.22
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• pp.18-23
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• 2005

Ships have been propelled and maneuvered by electrical drives since trle late seventies. Recently, rare earth PMs allow the design of brushless motors with very high efficiency over a wide speed range. This is the most important factor in ship propulsion technology. Several types PM motors have been developing for ship propulsion system. However these have disadvantage such as cogging torque. It causes an undesired effect that contributes to output ripple, vibration, and noise of machine. Therefore several techniques may be adopted in designing PM motor in order to reduce the cogging torque. This paper describes cogging torque receding methods such as adjusting arigap length, magnet arc, and magnet thickness. That are analysed by using the finite element method(FEM) and the maxwell stress tensor method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.533-534
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• 2006

In this paper we propose a new model of a mini-pump with peristaltic motion and present the results of the finite element analysis of an electromagnetic micro actuator. The mini-pump consists of three diaphrams made of PDMS, three permanent magnets in cylinders, printed copper coils on glass substrates, and input and output port. The size of the mini-pump is $14\;{\times}\;40\;{\times}\;5.4$ mm3 and the permanent magnet diameter 6.2 mm $\times$ thickness 2 mm. The electromagnetic force applied on the magnet was about 0.84 N when the current of coils was 1 A, then the maximum displacement of the PDMS diaphram was about 2mm.