• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.318-320
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• 2003

This paper presents a novel single-stage high frequency resonant DC-DC converter using zero voltage switching with high input power factor. The proposed high frequency resonant converter integrates half-bridge boost rectifier as power factor corrector (PFC) and half-bridge resonant converter into a single stage. The input stage of the half-bridge boost rectifier is working in discontinuous conduction mode(DCM) with constant duty cycle and variable switching frequency. So that a high power factor is achieved naturally. Simulation results through the Pspice have demonstrated the feasibility of the Proposed DC-DC converter. This proposed converter will be able to be practically used as a power supply in various fields as induction heating applications, DC-DC converter etc.

• 열처리공학회지
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• 제36권4호
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• pp.206-214
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• 2023

Tungsten carbide has many industrial applications due to its high electrical and thermal conductivity, high melting temperature, high hardness and good chemical stability. Because tungsten carbide is difficult to sinter, it is sintered with nickel or cobalt as a binder and is currently used in nozzles, cutting tools, and molds. Alumina is reported to be a viable binder for tungsten carbide due to its higher oxidation resistance and lower cost than nickel and cobalt. The ultrafine tungsten carbide-graphene-alumina composites were rapidly sintered in a high frequency induction heating active sintering unit. The microstructure and mechanical properties (fracture toughness and hardness) of the composites were investigated and analyzed by Vickers hardness tester and electron microscope. Since the high-frequency induction heating sintering method enables high-speed sintering, ultrafine composites can be prepared by preventing grain growth. In the tungsten carbide-graphene-alumina composites, the grain size of tungsten carbide increased with the amount of alumina participation. The hardness and fracture toughness of the tungsten carbide-5% graphene- x% alumina (x = 0, 5, 10,15) composites were 5.1, 8.6, 8.6, and 8.4 MPa-m^1/2 and 2384, 2168, 2165, and 2102 kg/mm², respectively. The fracture toughness increased without a significant decrease in hardness. Sinterability was improved by adding alumina to tungsten carbide-graphene.

• 전자공학회논문지
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• 제53권6호
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• pp.155-166
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• 2016

전자유도 가열시설에서 정밀하고 일정한 주파수 성분에 의해 가열물체에 발열을 유도하려면 LC공진회로 설계단계에서 출력 주파수에 대한 커패시터의 정전용량(C)과 워크코일의 유도계수(L) 설정이 중요하다. 하지만 고유의 발열계수를 가진 물체의 가열위치와 범위에 직접유도를 하는 워크코일은 고정적으로 설계되는 반면 커패시터는 가변되도록 설계되어야만 전체장비의 활용도가 높아진다. 본 논문에서는 $1000V_{MAX}$ 최대전압과 $200I_{MAX}$ 전류에서 최대 700kHz의 고주파 LC공진 출력이 되도록 커패시터 내부구성 원자재 선정 및 공정설계 단계까지 단일전극 용량별 샘플을 추출하였다. 그리고 정전용량 규격변화에 따라 주파수 변화특성과 출력 파라메타 결과를 바탕으로 HF-LC공진용 전도냉각 커패시터의 최적설계를 위한 관계를 증명하는 기초 실험결과를 제시하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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• pp.232-234
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• 2001

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 추계학술발표대회 개요집
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• pp.263-265
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• 2001

• 한국재료학회지
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• 제24권2호
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• pp.67-72
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• 2014

Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties, including high strength, high hardness, excellent ductility and toughness. In this study, nanopowders of $Al_2O_3$, MgO and $TiO_2$ were prepared as starting materials by high energy ball milling for the simultaneous synthesis and sintering of the nanostructured compound $Mg_4Al_2Ti_9O_{25}$ by high-frequency induction heating process. The highly dense nanostructured $Mg_4Al_2Ti_9O_{25}$ compound was produced within one minute by the simultaneous application of 80MPa pressure and induced current. The sintering behavior, grain size and mechanical properties of the $Mg_4Al_2Ti_9O_{25}$ compound were evaluated.

• 전기학회논문지P
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• 제64권4호
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• pp.261-266
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• 2015

This paper presents a newly proposed prototype of voltage-fed half-bridge partial resonant zero voltage switching PWM inverter operating at a constant frequency variable power regulation scheme, which is more suitable and acceptable for induction heated(IH) cooking appliances. This application-specific high frequency inverter circuit topology using a new generation specially-designed IGBTs can operate under a principle of a fixed frequency ZVS-PWM strategy. The operating principle of a new partial resonant inverter circuit is described on the basis of its computer-aided simulation analysis, its including steady-state operating characteristics.

• 자원리싸이클링
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• 제21권3호
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• pp.48-55
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• 2012

최근 친환경적이며 고효율적인 폐동선의 재활용을 위하여 다양한 방안이 모색되고 있는 실정이다. 본 연구에서는 폐동선의 고주파 유도가열을 이용하여 폐동선의 피복제거의 실험을 수행하여 폐동선의 친환경적이며 고효율의 재활용방안을 모색하고자 다양한 공정조건하에 최적화된 방안을 도출하였다. FT-IR 분석결과, 폐동선에 코팅된 물질은 polyester임이 나타났으며, 와전류의 전산모사결과, 최적화 과정을 도출하고 이에 대하여 논의하였다. 폐동선의 피복을 효과적으로 단시간에 분리하기 위하여 폐동선을 고주파 유도코일에 수직으로 장입하고 $950^{\circ}C$이상의 온도에서 유지해야 함을 알 수 있다.

• 한국가구학회지
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• 제16권2호
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• pp.59-65
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• 2005

As physical condition of students improves, there is a need to develop human body-friendly desk and chair for students. In this study, desks and chairs were manufactured with curved veneer lamination under high frequency heating and pressing, using ten wood species such as Japanese red pine, Korean pine, pitch pine, Japanese larch, yellow poplar, black locust, oak, radiata pine, beech, and birch. The performance of these products were evaluated. The results obtained were summarized as follows; With high frequency heating, the turned lamination of veneers with full size sheet ($3{\times}6\;feet$) prepared by rotary lathe peeling was successfully applied for making the members of desk top, leg frames of desk and chair. Bending strengths of desk tops were relatively greater for yellow poplar, black locust and red pine, which were similar to those of beech and birch. Bending strengths of desk legs were classified into greater species group (red pine, yellow poplar, larch) and lower species group (radiata pine, Korean pine, pitch pine). Compressive strengths of chair legs in parallel direction to the lamination were greater in black locust and larch. On the other hand, differences between outer and inner gap at the top and drawer bottom of desk top were rather larger for the laminations of birch and beech, and less for those of yellow poplar and pitch pine, showing greater stability of open drawer space. In results, yellow poplar, larch, pitch pine and red pine showed good appearance and strength properties at the curved veneer lamination. Accordingly, it was believed that these domestic woods were able to substitute for birch which was being imported for the use of veneer-laminates type furniture.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1251-1252
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• 2013