• Current Photovoltaic Research
• /
• 제6권2호
• /
• pp.39-42
• /
• 2018

When the PV module is illuminated in a high temperature region, solar cells are also exposed to the high temperature external environment. The operating temperature of the solar cell inside the module is increased, which causes the power drops. Various efforts have been made to reduce the operating temperature and compensate the power of solar cells according to the outdoor temperature such as installing of a cooling system. Researches have been also reported to lower the operating temperature of solar cells by improving the heat dissipation properties of the backsheet. In this study, we conducted a test to measure the internal temperature of each module components and the external temperature when the light was irradiated according to the surrounding temperature. Backsheets with different thermal conductivities were compared in the test. Finally, in order to explain the temperature difference between the solar cell and the outside of the module, we proposed an evaluation method of the heat transfer characteristics of photovoltaic modules with different backsheet.

• Journal of Power Electronics
• /
• 제18권4호
• /
• pp.1268-1277
• /
• 2018

A relatively high operating frequency is required for efficient wireless power transfer (WPT). However, the alternating current (AC) resistance of coils increases sharply with operating frequency, which possibly degrades overall efficiency. Hence, the evaluation of coil AC resistance is critical in selecting operating frequency to achieve good efficiency. For a Litz wire coil, AC resistance is attributed to the magnetic field, which leads to the skin effect, the proximity effect, and the corresponding conductive resistance and inductive resistance in the coil. A numerical calculation method based on the Biot-Savart law is proposed to calculate magnetic field strength over strands in Litz wire planar spiral coils to evaluate their AC resistance. An optimized frequency can be found to achieve the maximum efficiency of a WPT system based on the predicted resistance. Sample coils are manufactured to verify the resistance analysis method. A prototype WPT system is set up to conduct the experiments. The experiments show that the proposed method can accurately predict the AC resistance of Litz wire planar spiral coils and the optimized operating frequency for maximum efficiency.

• 전기학회논문지P
• /
• 제58권4호
• /
• pp.416-421
• /
• 2009

Recently, the new Korean Tilting Train Express(TTX) which maintains a speed on the curve railway line is developed. Electric railways, including the TTX, have electrical problems that could bring about serious accidents. For such reasons, the electric railway's electrical problems, electrical harmonic and others, have been studied briskly. Thus, TTX's electrical problems also need leading studies because the new Korean TTX will operate earnestly in 2012. The results could be used hereafter diagnosis of it's components and train conditions. In the paper, electrical signals in TTX operation were measured to analyze electrical harmonic. In addition, after the electrical signals were measured to operating mode (coasting mode, acceleration mode and regenerative breaking mode) respectively in test section(Ho-nam line, Chung-buk line, Jung-ang line and Tae-baek line). The electrical harmonics considered operating modes triparted were analysed and evaluated.

• 한국에너지공학회:학술대회논문집
• /
• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
• /
• pp.171-176
• /
• 1999

Nondestructive inspection and accompanying life analysis based on fracture mechanics were the major conventional methods for evaluating remaining life of critical high temperature components in power plants. By using these conventional methods, it has been difficult to perform in-service inspection for life prediction. Also, quantitative damage evaluation due to unexpected abrupt changes in operating temperature was almost impossible. Thus, many efforts have been made for evaluating remaining life during operation of the plants and predicting real-time life usage values based on the shape of structures, operating history, and material properties. In this study, a core software for on-line life monitoring system which carries out real-time life evaluation of a critical component in power boiler(high temperature steam headers) is developed. The software is capable of evaluating creep and fatigue life usage from the real-time stress data calculated by using temperature/stress transfer Green functions derived for the specific headers and by counting transient cycles. The major benefits of the developed software lie in determining future operating schedule, inspection interval, and replacement plan by monitoring real-time life usage based on prior operating history.

• 한국산학기술학회논문지
• /
• 제11권10호
• /
• pp.3885-3892
• /
• 2010

원자력발전소의 발전소보호계통과 같은 안전필수 시스템은 예상 가능한 사고로부터 인간과 자연을 보호하기 위한 중요 기능을 수행하는 시스템으로써, 어떠한 조건 하에서도 고유의 안전기능을 안정적으로 수행할 수 있도록 설계되어야 한다. 원자력발전소의 안전필수 기능을 수행하는 계측제어시스템에 적용되는 최신의 컴퓨터에는 다양한 하부기기를 감시 및 제어하고, 응용 프로그램을 실행시키기 위한 실시간 운영체제가 탑재되어 있으며, 이러한 실시간 운영체제는 가장 엄격한 소프트웨어 품질이 요구된다. 또한, 예상 가능한 조건에서도 안전필수 시스템의 기능이 적절히 수행될 수 있도록 설계, 분석 및 평가되어야 한다. 그러나 지금까지 국내 원자력발전소 안전필수 시스템에는, 원자력 기준과 품질등급에 따라 개발된 제품이 아닌 상용제품의 실시간 운영체제를 정성적 측면에서 승인(Commercial Grade Item Dedication)하는 방식으로 적용되어 왔다. 이로 인해 실시간 운영체제가 안전필수 기능을 수행하는 데 적합한지를 평가하는 상세 방법론과 경험이 매우 부족한 것으로 파악되고 있다. 특히, 안전필수 시스템에 적용함을 목적으로 신규 개발되는 실시간 운영체제의 경우, 안전성을 평가하기 위한 적절한 방법을 도출하기에 어려움이 있는 것으로 파악되고 있다. 본 논문에서는 원전의 안전필수 기능을 수행하는 실시간 운영체제의 설계요구사항을 기반으로, 안전필수 실시간 운영체제에 대한 안전성 분석 및 평가 사례를 제시하고자 한다. 본 논문에서 제시한 상세 안전성 평가의 방법과 사례는 향후 타 산업분야에서의 안전필수 실시간 운영체제 개발 및 안전성 평가에 활용될 수 있을 것으로 기대된다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.194-197
• /
• 2001

Traction motors driven by high speed switching inverters is demanded higher operating temperature, severe duty cycles, higher starting current, frequent voltage transients and finally severe environmental exposure. For applications to inverter duty, traction motors needs a special insulation system, which has characteristics of increased bond strength, lower operating temperature and higher turn-to-turn insulation. In this paper, design considerations and manufacturing procedure of 200 Class insulation system with polyimde(Kapton) main insulation and silicone resin VPI process on the traction motor for EMU will be reviewed. And performance test and long life evaluation test which prove stability and long life evaluation test which prove stability and reliability of insulation system for traction motor will be introduced.

• 한국안전학회지
• /
• 제25권6호
• /
• pp.186-196
• /
• 2010

It has been well known that traffic accidents occur under combined functional contributions of drivers, vehicles and road facilities, and that evaluation of safety levels for a specific road section or point is generally much complicated. Additionally, most of traffic accidents occur randomly implicating it is necessary to be evaluated in terms of probability theory. Thus, the evaluation model which reflects various characteristics and probabilistic distributions of traffic accidents has been necessary. The present paper provides a reliability based model with variables of probabilistic operating speeds and design speeds together which have been individually explaining associated characteristics in traffic accidents. Consequently, the model made it possible for speed management and road improvement projects to be evaluated in a common index. Application studies were performed in three cases. Through the studies, couples of facts were identified that the model successfully considered the probabilistic operating speeds and design speeds together and that then, the model evaluated road safety alternatives relatively which are complicatedly characterized and differently located.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2003년도 추계 학술발표회논문집
• /
• pp.66-73
• /
• 2003

The technique for the seismic reliability evaluation of the electric power network is presented. In the previous study, the state of the substations was represented by the bi-state which is classified as failure or survival. However, the hi-state model can result in oversimplified analysis, because substations are worked by the parallel operating system. In this paper, Considering the characteristics of the parallel operating system, the damage of the substation is expressed by the multi-state for the more realistic seismic reliability evaluation. Using Monte-Carlo simulation method, the seismic reliability for Korean 345㎸ electric power network is evaluated. Analysis results show that reliability levels of the network by the multi-state analysis is higher than that by the hi-state analysis and the electric power network in southeastern area of the Korean Peninsular may be vulnerable to earthquakes.

• 아동학회지
• /
• 제37권6호
• /
• pp.119-132
• /
• 2016

Objective: The purpose of this study was to analyze the operation and personal information management of public and private kindergarten homepages. Methods: A total of 2,846 kindergartens were selected from the I-Sarang portal service for analyzing operation, and 217 self-operating homepages were selected for evaluating management. Seven evaluation items from three domains (information gathering procedures and scope, information security, and management of file exposure protection) were used. Wireshark and Google were used for analyzing some evaluation items. Results: The operating ratio of kindergarten homepages was low and most of the kindergartens self-operated their homepages. The evaluation of the information gathering procedures and scope showed that the rule of consent process was not rigidly followed but that the rule of legality for information gathering was followed. Items related to information security were followed at very low levels. As for the management of file exposure protection, the evaluation of items related to the prevention of attachment disclosure showed that the rule of protecting personal information included in an attached file was followed but that the notice regarding information protection was not. Across all evaluation items, the level of personal information management was higher in public (vs. private) kindergartens. Conclusion: These results indicate methods to more securely and effectively manage personal information on kindergarten homepages.

• 한국군사과학기술학회지
• /
• 제16권3호
• /
• pp.260-267
• /
• 2013

A combat system for navy's battleship is a system of systems who supports naval indigenous operations by integrating and inter-operating many different kind of weapon and non-weapon systems, which has characteristics of large-scale complex computing system. This paper considers a characteristics of naval combat system which has been developed by domestic technology and suggests a way to improve future naval combat system in terms of computing architecture by applying commercial real-time operating system technologies. This paper also provides an evaluation criteria for combat system adaptability of real-time operating systems.