• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1389-1390
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• 2007

SF6 gas used widely as insulating component is rising as the environment problem. Electrical breakdown characteristics of epoxy and dry-air composite insulation was investigated on thickness of epoxy and pressure of dry-air under non-uniform field. The gap of needle to plane was from 2mm to 5mm. The pressure of dry-air was varied within the range of $0.1{\sim}0.6$ MPa. The thickness of a needle was 1mm and the curvature radius of a needle end was 100um. The diameter of a plane made of the stainless steel was 50mm. As a result of the experiment, breakdown voltage was increased about 3 times when epoxy was used. The impact that the thickness of epoxy influences on breakdown voltage was poor. It needs suitable thickness computation because the insulating gap of the gas is short as epoxy thickness increases.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.118-120
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• 2006

This paper proposes a new stator pole shape having non-uniform air-gap in order to minimize the undesirable torque ripple of switched reluctance motor(SRM). Through numerical analysis using finite element method(FEM) and optimization, the proposed pole-shape-optimized stator is proven to give reduced torque ripple.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.4
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• pp.257-267
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• 1990

A numerical and experimental investigation has been carried out to understand a characteristic of natural convection within a horizontal non-circular annulus. A finite-difference method has been used to solve the governing equations numerically. The effect of Rayleigh number. Prandtl number, aspect ratio and diameter ratio is studied analytically. The ranges of the parameters studied herein are Rayleigh number from $10^3$ to $2{\times}10^4$, Prandtl number from 0.1 to 10, aspect ratio from 0.25 to 1.5 and diameter ratio from 1.5 to 9.0. A Mach-Zehnder interferometer is used to obtain isothermal fringes for a diameter ratio Do/Di=2.6 and aspect ratio H/L=0.75 experimentally. A comparison between the experimental and numerical results under similar conditions shows good agreement.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.40-44
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• 2013

This paper presents a design and characteristics analysis of novel 2-phase 4/3 switched reluctance motor (SRM) with short flux path for an air-blower application. The desired air-blower is unidirectional application, and requires a wide positive torque region without torque dead-zone. In order to get a wide positive torque region without torque dead-zone during phase commutation, asymmetric inductance characteristic with non-uniform air-gap is considered. The proposed motor could be started at any rotor position with high efficiency drive. The proposed 2-phase 4/3 SRM is verified by finite element method analysis.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.2
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• pp.132-139
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• 2001

We considered the uniformity of fabricated micromirror arrays by characterizing the fabrication process and calculating the appropriate driving voltages of micromirrors used as virtual photomask in maskless photolithography. The uniformity of the micromirror array in terms of driving voltage and optical characteristics is adversely affected by factors, such as the air gap between the bottom electrode and the mirror plate, the spring shape and the deformation of the mirror plate or torsion spring. The thickness deviation of the photoresist sacrificial layer, the misalignment between mirror plate and bottom electrode, the aluminum deposition condition used to produce the spring and the mirror plate, and initial mirror deflection were identified as key factors. Their importance lies in the fact that they are related to air gap deviations under the mirror plate, asymmetric driving voltages in left and right mirror directions, and the deformation of the Al sring or mirror plate after removal of the sacrificial layer. The plasma ashing conditions used for removing the sacrificial layer also contributed to the deformation of the mirror plate and spring. Driving voltages were calculated for the pixel operation of the micromirror array, and the non-uniform characteristics of fabricated micromirrors were taken into consideration to improve driving performance reliability.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.673-675
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• 2015

This paper presents a design of a high speed 2-phase 6/5 switched reluctance motor (SRM) for an air-blower application. This type of motor is suitable for the applications that require high speed and only one directional rotation as air-blower. The desired air-blower is unidirectional application, and requires a wide positive torque region without torque dead-zone. In order to get a wide positive torque region without torque dead-zone during phase commutation, asymmetric inductance characteristic with non-uniform air-gap is considered. The proposed motor can be operated at any rotor position. The proposed 6/5 SRM uses short flux path technique that achieved by means of winding configuration and lamination geometry. The purpose of short flux path is to reduce the core loss and the absorption MMF in the stator. The proposed 2-phase 6/5 SRM is verified by finite element method (FEM) analysis and Matlab-Simulink. In order to verify the design, a prototype of the proposed motor was manufactured for practical system.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.101-102
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• 2008

SF6 widely used as insulating gas is rising as the environment problem. For decreasing this greenhouse gas, electrical breakdown characteristics of vacuum with air are studied in non-uniform field. The gap of needle to plane was 0.5mm. The pressure of vacuum the range of 10^-4${\sim}$10^-5torr. The diameter of a plane made of the stainless steel is 150mm. As a result of the experiment, the breakdown voltage is increased about degree of vacuum increased. The electrode material influenced breakdown voltage in vacuum.

• Journal of Magnetics
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• v.19 no.4
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• pp.411-417
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• 2014

This paper presents the shape optimization of a permanent magnet synchronous motor to reduce the torque ripple and iron loss. Specifically, the harmonics of the electromotive force and cogging torque are decreased by adjusting the permanent magnet arrangement and non-uniform air gap length. In addition, an additional flux path along the q-axis is proposed with a unique rotor shape to increase the q-axis inductance and reluctance torque. The improvement in the performance of the proposed model is verified with simulated and experimental results.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.9-15
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• 2013

This paper presents a uniform analytical model by energy method and Fourier series expansion to analyze detent force in uneven magnetic field for permanent magnet linear synchronous motor (PMLSM). The model reveals that detent force in long-primary type is mainly influenced by non-ideal distribution of permanent magnet magnetic motive force, while nounified air-gap permeance makes a great impact on detent force of short-primary type. Hence, magnetic field similarity of motor design techniques referring rotary counterpart are adopted. For long-primary type novel method of splitting edge magnets is proposed to reduce end effects force, and optimal widths of edge tooth in short-primary type also verify the effectiveness of magnetic field similarity. The experimental results validate finite element analysis results.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.734-736
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• 2015

본 논문은 비균일 공극형 단상 4/4극 하이브리드 스위치드릴럭턴스 전동기(이하, HSRM)를 제안한다. 제안된 HSRM의 회전자 형상은 비균일한 공극을 갖는 형상으로 데드존 구간과 토크리플, 출력특성에 기여한다. 이와 같은 특성을 검증하기 위해 균일한 공극을 갖는 단상 하이브리드 SRM의 토크 및 출력특성을 유한요소해석(FEA)을 통해 비교하였다. 그 결과 제안된 HSRM을 제작하였고 시험 결과를 통해 그 타당성을 검증하였다.