• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.4
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• pp.341-349
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• 2004

A parallel operation of Uninterruptible Power Supply(UPS) systems is used to increase power capacity of the system or to secure higher reliability at critical loads. In the conventional parallel operation, the load-sharing control to maintain the current balance is the most important, since the load-sharing is very sensitive to discord between components of each module, amplitude/phase difference, line impedance, output LC filter, and so on. To solve these problems various control algorithms are researching. However, these methods cannot apply to the different ratings of UPS. In the case, master and slave control algorithm for parallel operation is adequate. However, if the UPS ratings are different, the value of passive filters L, C is different, and it affects the sharing of current. This paper presents general problems of conventional parallel operation systems, and control strategy for parallel operation with different ratings. The validity of the proposed control strategy is investigated through simulation and experiment in the parallel operation system with two 3-phase UPS systems.

• Fire Science and Engineering
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• v.22 no.1
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• pp.24-28
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• 2008

This paper studied on the causal analysis of electrical fire by using fuse that it is used with safety device in electrical products. The experimental samples used are glass tube fuse(15 A, $5{\times}20mm$) and temperature fuse(10 A, $72^{\circ}C$). The experiment analyzed on the characteristics of damaged fuse by main causes(short circuit, overload, external flame) of electrical fire. The results showed, in case of glass tube fuse identified different characteristics in external form and element surface and element texture of damaged fuse by main causes of electrical fire. In case of temperature fuse identified different characteristics in external form and sliding contact surface and sliding contact texture of damaged fuse only by external flame.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.12
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• pp.78-84
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• 2009

When external force is applied to humanoid robot's head, humanoid robot's neck is rotated to prevent the damage of it. So, robot's neck have to perceive forces (Fx of x-direction, Fy of y-direction and Fz of z-direction) and moments (Mx of x-direction, My of y-direction and Mz of z-direction) using the attached 6-axis force/moment sensor. Thus, in this paper, 6-axis force/moment sensor was developed to sense the forces and moments applied to robot's head. The structure of 6-axis force/moment sensor was modeled newly, and it was designed using FEM software (ANSYS) and manufactured by attaching straingages on the sensing element, finally, the characteristic test of the sensor was carried out. As a result, it is confirmed that interference error is less than 3%. And, it is thought that the sensor can be used to measure the forces and the moments for humanoid robot's head.

• Proceedings of the KIEE Conference
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• summer
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• pp.1172-1175
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• 2004

포항 방사광 가속기의 선형가속기는 2.5GeV 전자빔용 마이크로웨이브의 발생을 위하여 80 MW급 클라이스트론(klystron) 11대와 입사부용 65 MW 급 클라이스트론 1대를 사용한다. 80 MW 급 클라이스트론 부하를 구동하기 위하여 최대 펄스 정격출력 200MW(400kV, 500A, 평탄도 $4.4\;{\mu}s$)인 대출력 펄스 전원공급 장치(modulator)가 요구된다. 모듈레이터 시스템 용 PFN(pulse forming network) 커패시터의 충전용 입력전원으로써 최대 출력전압 50 kV, ${\pm}\;0.5\%$ 이내의 전압제어가 가능한 고전압 인버터 전원장치를 적용하여 PLS 선형가속기용 국산화 개발 클라이스트론 부하의 성능시험을 수행하였다. 국산화 개발된 S-band 펄스 클라이스트론은 고전압 길들이기 과정을 거쳐 최대 정격 출력 빔 전압 400 kV 이상까지 시험 완료하였다. 클라이스트론의 정확한 RF 출력성능의 측정을 위하여 방향성 결합기와 검파기를 설치하여 측정시스템의 성능을 개선하였다. 본 논문에서는 포항 방사광 가속기의 국산화 개발 1호 클라이스트론 부하의 성능시험을 위한 50 kV 급 인버터시스템 적용과정에서 수행하였던 시험장치 개선과 PFN의 충전 특성을 분석하였다. 또한, 클라이스트론의 고전압 및 RF 길들이기 시험 결과에 관하여 고찰하고자 한다.

• Proceedings of the KIEE Conference
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• summer
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• pp.1519-1521
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• 2004

포항풍력에너지연구소와 (주)보국전기는 에너지 관리공단의 지원으로 2002년부터 직접구동형 풍력 터빈 KBP-750D에 사용될 발전기를 개발해 오고 있다. KBP-750D에 사용되는 발전기는 증속을 위한 gearbox를 사용하지 않는 직접 구동형 이라는 것과, 영구자석을 사용하여 여자하는 형식이라는 것이다. 이런 특징은 풍력발전에서 요구하는 주요 요구조건인 고효율, 고신뢰성을 만족시키기 위해서 매우 중요하다. 개발된 발전기는 25 rpm 정격에서 800 kW의 정격을 가지도록 설계되었다. 공극 직경은 3,320 mm 이며, stator의 길이는 705 mm, 4.5 mm의 공극, 84극을 가지고 있으며, 전체중량은 약 20 ton이다. 이 보고에서는 이 발전기의 물리설계 공학설계 등에 관해서 논의한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.496-503
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• 2003

SFC system has come to be used as drive large synchronous machine in many industry applications. Many papers have been presented on the control algorithm of SFC system, not the acceleration and start-up but the rated speed operation with line connection and the braking operation with regeneration which is used in the industry. This paper presents the whole section control algorithm for a large synchronous machine using SFC system. The results of experiment show that the proposed algorithm is proper and effective.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.1
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• pp.11-15
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• 2019

Recently, the circuit-breaker rated voltage is getting higher as the transmission voltage increases. To increase the circuit-breaker rated voltage, a multi-break circuit-breaker which has two or more breakers in series is adopted. For multi-break circuit-breaker, a grading capacitor is used to mitigate the Transient Recovery Voltage(TRV) and control the voltage distribution across the individual interrupter units. However, all over the world, there are many failures such as mechanical damage, explosion due to insulation breakdown. Therefore, it is necessary to study the causes of failure and the new performance verification method. In this paper, we investigate the causes of dielectric breakdown of the grading capacitors in the KEPCO power system and propose the performance verification method.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.81-92
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• 2013

The satellite includes many release mechanisms such as solar array deployment, antenna deployment, cover to protect contamination in scientific equipment, pyro value of the propulsion subsytem, and bypass device in Li-Ion cell module. A drive the initiators is a critical to the successful mission because the initiators of release mechanism driving by the pyrotechnic circuit is operated in single short. The pyrotechnic circuit has to provide switching network for safety. A typical switching network has defect consisting of high current rating fire switch to handle switching transient current during fire the initiator. The pyrotechnic circuit is required some form of power conditioning to reduce the peak power demanded from the bus if the initiators are to be fired from the main bus. This paper design a pyrotechnic circuit synchronized to the fire-command to activate the fire switch to overcome use high current rating fire switch to handle switching transient current during fire the initiator. The pyrotechnic circuit provides a current limited widow pulse for fire current synchronized to the fire-command to insure that fire switch will only carry the current but never switch it. The current limited widow pulse for fire current can be possible to use low current rating and light mass switch in switching network. The current limit function in the pyrotechnic circuit reduces supply voltage to initiator and provides the effect of power conditioning function to reduce peak bus power. The pyrotechnic circuit to apply satellite development on geostationary orbit is verified the function by test in development model.

• Fire Science and Engineering
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• v.34 no.3
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• pp.67-75
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• 2020

In this study, the risk of heat generation due to normal and overload currents that vary with the abnormal loosening angle of wire-connecting bolts were identified. The risks were analyzed based on the thermal characteristics to minimize the carbonization accidents of terminal blocks inside distribution panels typically used in industrial sites. We applied a method for measuring the heating temperature and temperature variations in the terminal blocks in real-time by installing a resistance temperature detector sensor board in the terminal block. The experimental results showed that the terminal block model with a low-rated current exhibited a higher heating temperature, thus, confirming the need to select the terminal block capacity based on load currents. Additionally, the higher the rated current of the terminal block with a high-rated current and the higher the degree of loosening, the faster the carbonization point. Such heating temperature monitoring enabled real-time thermal temperature measurement and a step-by-step risk level setting through thermal analysis. The results of the measurement and analysis of carbonization risks can provide a theoretical basis for further research regarding the risk of fire due to carbonization. Furthermore, the deterioration measurement method using the temperature sensor board developed in this study is widely applicable to prevent fires caused by poor electrical contact as well as risk-level management.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.259-261
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• 2001

전차 선로용으로 적용되는 직류 피뢰기의 설계 기술을 소개하였다. 현재 국내에 사용되는 전차 선로 서지 보호용 직류 피뢰기는 전량 수입에 의존하고 있다. 안전한 피뢰기를 설계하기 위해서 적용 구간의 임펄스 서지 환경을 파악하고 이에 맞는 적절한 내량의 피뢰기를 설계하는 것이 요구된다. 특히 직류 구간의 경우 과도 서지 발생의 형태가 기존 계통 환경과 다르기 때문에 피뢰기 보호범위와 정격의 설정에 주의가 요구된다.