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김두현,김성철,이종호,강문수,정천기,Kim, Doo Hyun,Kim, Sung Chul,Lee, Jong Ho,Kang, Moon Soo,Jeong, Cheon Kee 한국안전학회 2021 한국안전학회지 Vol.36 No.2
This paper presents the robust design of each component used in the development of an induction bolt heating system for dismantling the high-temperature high-pressure casing heating bolts of turbines in power plants. The induction bolt heating system comprises seven assemblies, namely AC breaker, AC filter, inverter, transformer, work coil, cable, and CT/PT. For each of these assemblies, the various failure modes are identified by the failure mode and effects analysis (FMEA) method, and the causes and effects of these failure modes are presented. In addition, the risk priority numbers are deduced for the individual parts. To ensure robust design, the insulated-gate bipolar transistor (IGBT), switched-mode power supply (SMPS), C/T (adjusting current), capacitor, and coupling are selected. The IGBT is changed to a field-effect transistor (FET) to enhance the voltage applied to the induction heating system, and a dual-safety device is added to the SMPS. For C/T (adjusting current), the turns ratio is adjusted to ensure an appropriate amount of induced current. The capacitor is replaced by a product with heat resistance and durability; further, coupling with a water-resistant structure is improved such that the connecting parts are not easily destroyed. The ground connection is chosen for management priority.
FTA를 이용한 볼트 유도가열시스템의 고장 및 전기화재 분석
김두현,김성철,엄한얼,강문수,정천기,Kim, Doo-Hyun,Kim, Sung-Chul,Eom, Haneol,Kang, Moon-Soo,Jeong, Cheon-Kee 한국안전학회 2021 한국안전학회지 Vol.36 No.4
This paper presents a safety assessment method for FTA-based induction heating systems; the failures and causes of electrical fire are first analyzed for each part and module qualitatively, and methods to manage high probabilities of failure and electrical fire are considered, thereby improving the reliability of the induction heating system. The cumulative importance value (ACC) of the minimal cut set is drawn by setting failure as the top event, and STACK and SMPS are observed to account for about 70% of the induction heating system failures. Thus, intensively managing the basic events contained in the minimal cut set of failures for STACK and SMPS is expected to provide effective and stable operation of the induction heating system. When electrical fire is set as the top event, the STACK percentage is 90%. Accordingly, the current IGBT is changed to a FET to increase the applied voltage and prevent induction heating system failure, and a heat sink plane is installed to prevent FET heating caused by switching, thereby preventing an electrical fire. By classifying the parts and modules of the induction heating system in detail and by applying FTA based on actual failure rates and relevant data, more practical and reasonable results may be expected. Hence, continuous research must be conducted to ensure safety when using induction heating systems.
태양광발전기와 변속기를 장착한 저속 전기차의 개발과 활용
엄기증(Gi Jeung Um),정천기(Cheon-Kee Jeong),신광문(Kwang Mun Shin) 한국에너지기후변화학회 2019 한국에너지기후변화학회 학술대회 Vol.2019 No.11
At present, major countries in the world are actively pursuing environmentally friendly automobiles to improve the air quality and reduce oil consumption for national security. In addition, interest in low-speed electric vehicles (NEV) is increasing due to the steady increase of single-person households and the incidence of near-field mobility in farming, fishing villages, and urban areas. [Speed <= 60km/h, Weight <= 1,361kg (Including batteries)] Currently, most low-speed electric vehicles in developed countries such as the US use 72V (12V×6) of battery power and operate at maximum speed (40km/h) and mileage (30 ~ 50km) / 1 time charging. Charging time (4~6 hours), battery life (about 1,000 cycles), lowest price (approx. 12 million won), low-speed charging method using single-phase power for home is the mainstream. It has been pointed out that the decrease in energy efficiency of vehicles can be a limiting factor for the expansion of supply. Given the low-speed EV market, which is expected to continue to grow in the future, real-time charging (RTC) while moving and stopping enhances user convenience, improves access to insufficient charging infrastructure, and extends life, distributes power. There is a need to improve the energy efficiency of the entire low-speed electric vehicle (NEV) system using an improved transmission and solar charging device.
FTA를 적용한 태양광 발전 및 ESS 연계형 PCS의 안전성 평가
김두현 ( Doo-hyun Kim ),김성철 ( Sung-chul Kim ),김의식 ( Eui-sik Kim ),남기공 ( Ki-gong Nam ),정천기 ( Cheon-kee Jeong ) 한국안전학회(구 한국산업안전학회) 2019 한국안전학회지 Vol.34 No.1
This paper presents a safety assessment based approach for the safe operation for PCS(Power Conditioning System) of photovoltaic and energy storage systems, applying FTA. The approach established top events as power outage and a failure likely to cause the largest damage among the potential risks of PCS. Then the Minimal Cut Set (MCS) and the importance of basic events were analyzed for implementing risk assessment. To cope with the objects, the components and their functions of PCS were categorized. To calculate the MCS frequency based on IEEE J Photovolt 2013, IEEE Std. 493-2007 and RAC (EPRD, NPRD), the failure rate and failure mode were produced regarding the basic events. In order to analyze the top event of failure and power outage, it was assumed that failures occurred in DC breaker, AC breaker, SMPS, DC filter, Inverter, CT, PT, DSP board, HMI, AC reactor, MC and EMI filter and Fault Tree was drawn. It is expected that the MCS and the importance of basic event resulting from this study will help find and remove the causes of failure and power outage in PCS for efficient safety management.