• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.171-173
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• 2016

일반적으로 대형 버스 및 트럭 등 같은 경우, 부하가 아주 크다. 또한 내리막길이나 장거리 운행 시에 잦은 제동으로 인하여 마찰을 이용한 기존 방식의 브레이크들은 브레이크 파열 및 페이드 현상 때문에 제동 안전성에 문제가 있다. 이러한 제동 부담을 분담하기 위해 현재 보조브레이크(리타더)가 필수적이며, 엔진 계통의 보조브레이크가 아닌 비접촉식 브레이크 같은 친환경 보조브레이크가 요구되고 있다. 그리고 차량 제동시 발생하는 기계에너지를 전기에너지로 회생하여 에너지효율을 향상시키려는 연구가 현재 활발히 진행되고 있다. 본 논문에서는 와전류를 이용한 전자기형 리타더에서 발생되는 전기에너지를 회수하기 위한 전압 제어 방법을 다룰 것이다. 리타더의 제동에너지를 전기에너지로 회생하기 위해 L-C 공진회로로 구성하였다. 리타더를 자여자 유도발전기(Self-Excited Induction Generator)로 모델링 하였고 이를 토대로 시뮬레이션 및 실험을 진행하였다. 자여자 유도발전기의 구동 조건에 대해서 언급하고 이를 파라미터에 따라 3-D map으로 만들었다. 또 회로 중의 FET 게이트에 전압을 인가하는 제어장치의 구동펄스에 따라 바뀌는 공진회로의 전압을 분석하였으며, 이 전압을 제어하기 위하여 PI 제어기를 이용한 알고리즘을 제안하였다. 이 전압을 3상 AC/DC컨버터를 통과한 후 DC/DC컨버터를 통하여 차량 내부의 배터리에 충전되는데 제어를 위해 3상 AC/DC에서의 전압 리플을 MA(Moving Average) 방식의 필터를 사용하여 DC/DC컨버터의 입력에 맞도록 제어하였다. 이와 같이 전자기형 리타더에서 유도되는 전압을 제어기의 제어 펄스에 따라 제어할 수 있으며 Matlab Simulink를 이용하여 리타더의 모델과 그 제어기의 타당성을 보였다. 또 실제 M-G Set 실험을 통하여 그 연관성을 확인하였다.

• Journal of the Korean Society for Railway
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• v.11 no.5
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• pp.477-481
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• 2008

This paper dealt with a detection method of series arc existence which is a symptom of electric fires in low-voltage system. The proposed detection circuit consists of a high-pass filter with a low cut-off frequency of 3kHz to attenuate power frequency voltage by 80 dB and an active band-pass filter with a center frequency of 4kHz to detect only the series arc signals. The performance of the circuit was evaluated in a phase-controlled incandescent lamp as a non-linear load and an inverted-fed induction motor as a high frequency load by using the arc generator specified in UL1699. From the experimental results, it was confirmed that the proposed method solved the detection error, which is being the most problem, by discriminating the series arc signal even in non-linear and high frequency loads.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.85-91
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• 2011

Alnico magnets can be used as magnetic bearings for the precise electric power measuring instruments such as watt-hour meters because they have high remanence ($B_r$), relatively high maximum energy product ($(BH)_{max}$), and excellent temperature stability. In this study, Alnico composite magnets were fabricated by appropriately mixing alnico alloy powders with epoxy resin and binder. The Alnico powders mixed with epoxy resin and a hardening agent with a mixing ratio of 96:4 were pressed and then cured to be a toroid-type ring magnet with an outer diameter (${\Phi}_{out}$) of 15 mm, an inner diameter (${\Phi}_{in}$) of 6.5 mm and a thickness (t) of 2.5 mm, respectively. The magnetic properties of the Alnico ring magnets were varied with the mixing ratio of Alnico powders that possess different average particle sizes. The Alnico ring magnet prepared by mixing 5 wt% of $50{\mu}m$ (small size) powder, 15~20 wt% of $150{\mu}m$ (medium size) powder, and 75~80 wt% of $300{\mu}m$ (large size) powder showed the best magnetic properties (remanent induction, coercive force, maximum energy product, and surface flux density). In addition, measurements of temperature and moisture characteristics for the Alnico ring magnets showed that the surface flux densities of the N and S poles decreased little and the repulsive distance between the magnets decreased as small as 0.05 mm after 10 days.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.4
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• pp.117-122
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• 2021

Permanent magnet synchronous motors can secure high power density and efficiency, but have problems in that the materials required for manufacturing are expensive and design is somewhat more difficult than induction motors. Therefore, it is necessary to develop an optimal motor that considers both efficiency and maintenance convenience and related control research. In addition, driving by a practical motor leads to a request to increase the highest efficiency in a narrow rated range, an increase in average efficiency in the entire electric driving range, and an increase in average output. Due to this movement, a reluctance motor that does not require a permanent magnet is being considered as an alternative. In this paper, in line with the issues of the times that require the development of future technology that can replace rare earth permanent magnet motors and the technological preemption of rare earth reduction motors and rare earth motors, switched reluctance motors without permanent magnet For motor, SRM), modeling through machine language (C language) and the characteristics of SRM accordingly are to be studied.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.219-226
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• 2022

In this experimental study, the effect of continuously changing the position of electromagnetic force using several coils and a relay switch on fracture energy was investigated. Normal mortar and steel slag mortar specimens in which 50 % and 100 % of sand was replaced with steel slag were cast and exposed to electromagnetic field. The electric field was induced by one coil without a relay switch as an existing method and by partitioning the coil and continuously changing the position using a relay switch. The fracture energy was calculated from the load-vertical displacement curve obtained from the experiment and compared with each other. As a result of the experiment, it was confirmed that the method of partitioning the coil and changing the position of electromagnetic force by using a relay switch is effective in increasing the fracture energy even if the same amount of power is used.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.148-156
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• 1994

Three composition in the system of $YO_{1.5}-BaO-CuO$ were grown using a cold crucible (skull) melting technique with a 50 kW R.F. induction generator operating at 4 MHz as the power source. The starting materials were prepared by conventional ceramic powder processing methods, loaded into the skull, and melted at about $1200^{\circ}C$. For this study, compositions near the $YBa_2Cu_3O_X$ region were selected. The growth rates used ranged from 4 cm/hr to 0.25 cm/hr. The relation between the microstructures and the starting composition of each ingot was determined using metallograph, X-ray diffraction, and energy dispersive X-ray analysis. Both $YBa_2Cu_3O_X$ and $Y_2BaCuO_5$ needle-shaped crystals, aligned with the growth direction, were formed in the $CuO-BaCuO_2$ eutectic matrix of the $YBa_2Cu_7O_x and YBa_5Cu_{11}O_x$ ingot.

• Korean Journal of Environmental Agriculture
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• v.18 no.1
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• pp.41-47
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• 1999

To investigate the combined effect of gamma ray irradiation and NaCl treatment on Tradescantia somatic cell pink mutations, potted plants of Tradescantia 4430 were evenly sprayed with NaCl solution(170mM) 24 hours before irradiation(NaCl+${\gamma}$) and after irradiation(${\gamma}$+NaCl). Irradiation doses were 0.3, 0.5, 1.0 and 2.0 Gy of gamma-ray. The plants irradiated only with gamma radiation were used as control group(CT). Frequency of pink mutation increased linearly with irradiation close and the peak interval of elevated mutation frequencies appeared during 6∼12 days aver irradiation in all the experimental groups. The slope of dose-response curve in CT was 5.99($r^2$=0.99), while it were 4.55($r^2$=0.98) in NaCl+${\gamma}$ and 4.33($r^2$=0.99) in ${\gamma}$+NaCl. It seemed that pre- and post-treatment of NaCl had a protective effect it against radiation-induced cell damages since it decreased the slope value by more than 24%. It is suggested that protective effect on DNA damages can be invoked in irradiated stamen hair cells by NaCl treatment.

• Korean Journal of Food Science and Technology
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• v.52 no.1
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• pp.60-66
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• 2020

This study examined the antioxidant activity and neuroprotective effects of ethanol extracts obtained from Diospyros kaki core (DCE). The total polyphenol and flavonoid contents in DCE was 786.47±15.27 and 31.14±0.82 mg/g, respectively. In addition, DCE exhibited a dose-dependent induction of radical scavenging activity, determined by 1,1-diphenyl-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonicacid) (ABTS), ferric reducing antioxidant power (FRAP), and reducing power assays. The viability of HT22 hippocampal cells was examined to investigate the neuroprotective effect of DCE. DCE treatment did not induce cytotoxicity at concentrations below 1,000 ㎍/mL. Additionally, DCE treatment in the background of H₂O₂ induce oxidative stress revealed a significant increase in the survival rat, indicated by increased SOD activity and decreased levels of MDA, a lipid peroxidation product. Therefore, the results suggest that DCE can be used as a source of natural antioxidants source and a therapeutic agent for the treatment of brain disorders induced by oxidative stress and neuronal damage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.977-983
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• 2007

Recently, the number of systems which utilize wireless power transmission to a receiving module in a short distance is increasing. For efficient use of receiving space, coils are wound around the ferrite core to produce electromotive force(emf) in suppling power by wireless transmission. This paper analyzed the magnetic flux density distribution in the ferrite core in magnetic field environment which is uniformly oriented along to a single axis at 125kHz. For numerical analysis, Ansoft Maxwell which is applying the FEM(Finite Element Method) method was used. We studied the variations of the gathered magnetic fluxes to the changes of the relative permeabilities of the ferrite cores. Also we calculated the magnetic flux variation by shaving the ferrite core off for the groove of coil winding. Results showed that using a small ferrite core in magnetic field at 100kHz band can increase the amount of magnetic flux $3{\sim}4 times$ than without the core. The magnetic flux decreased 23% by shaving the core 0.5 mm on the periphery of 4.75 mm radius core with the relative permeability 800.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.2 no.1
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• pp.133-151
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• 2007

In the era of 21st new century. reinforcement of regional competitiveness by establishing innovation system is taking its place of main small and medium sized enterprise policies in major developed countries. The model of regional balanced development for promoting small and medium sized enterprise is a main frame of governmental small and medium sized enterprise policies. which complements national innovation process. And in the level of local area, the model is regional network system, molded in the process of induction, application, modification, proliferation of new technologies and knowledge by local businessman and innovators. This study focused on the strategy development for small and medium sized businesses to increase local competitive power, in terms of regional balanced development. In order to find the real problems and improvement alternatives for local competitive power, this study both reviewed the common strategies and action programs advanced in developed countries for small businesses, and did research on the current economic conditions in local area. Based on the lessons from foreign cases and the analysis of the current situations in small business in local area, the study suggested the model of regional balanced development for promoting small and medium sized enterprise including formation of innovation network system through the invitation of leading firms in the area, industry-university partnerships, and development and attraction for small and medium sized businesses.