• 한국정밀공학회지
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• 제25권2호
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• pp.49-56
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• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is a combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. In this paper the effect of transformer is studied. Multiple closed loop controllers with displacement feedback of variable pump/motor, speed feedback and position feedback of cylinder are used. The efficiency and energy consumption when cylinder is driven up and down is calculated by simulation. Simulation results show that considerable energy saving is achieved by choosing load ratio, circuit type and supply pressure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.917-922
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• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented. From simulation results, the disturbances including nonlinear friction torque, leakage flow and load force can be compensated and good positioning accuracy is obtained. It show that the proposed controller is effective.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1075-1080
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• 2007

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is a combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. In this paper the effect of transformer is studied. Multiple closed loop controllers with displacement feedback of variable pump/motor, speed feedback and position feedback of cylinder are used. The efficiency and energy consumption when cylinder is driven up and down is calculated by simulation. Simulation results show that considerable energy saving is achieved by choosing load ratio, circuit type and supply pressure.

• 한국전기전자재료학회논문지
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• 제23권11호
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• pp.880-885
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• 2010

The Angle Ring and Cap which is called pressboard are settled at the primary and secondary coil winding of 154 kV transformer that can reduce effectively distance of insulation. As it has not manufactured pressboard of Angle Ring and Cap for high voltage grade, insulation components industry especially high voltage transformer has not participate in a competition with worldwide yet. That's why is difficult to make an specialized shape of insulation components of high voltage grade. Therefore it has finally completed to make an deformation manufacturing utility using an bellowed special analysis tools. This study that uses various analysis program determining optimum shape about insulation of Angle Ring and Cap which is related life of high voltage transformer. In addition to develop forming equipment with an specialized five steps pressing. That is also based on the mechanical strength evaluation and test, it is investigated optimized processing components.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.30-30
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• 2010

The Angle Ring and Cap which is called pressboard are settled at primary and secondary coil winding of 154 kV transformer that can reduce effectively distance of insulation. As it has not manufactured pressboard of Angle Ring and Cap for high voltage grade, insulation components industry especially high voltage transformer has not participate in a competition with worldwide yet. That's why is difficult to make an specialized shape of insulation components of high voltage grade. At first, it is very important to make an utility of deformation manufacturing for high voltage transformer insulation components by itself. Therefore it has finally completed to make an deformation manufacturing utility using an special analysis tools. In this paper, developed insulation components was investigates in tensile strength is introduced.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.509-512
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• 2015

본 논문에서는 유압 실린더내의 피스톤 위치를 측정하기 위한 정전용량 센서(Capacitive Sensor) 구조를 연구하였다. 기존에 유압 실린더 내 피스톤 위치 측정을 위해 인덕티브(Inductive) 방식을 응용한 LVDT(Linear Variable Differential Transformer) 센서가 사용되고 있으며, 높은 정확도를 갖지만, 고가이며 구조적으로 복잡하다는 단점이 있다. 본 논문에서는 이러한 단점을 극복하기 위한 방법으로 유압실린더 내 최적화된 구조를 바탕으로 여러 가지 비접촉 정전용량 센서 구조 방식을 연구하였다. 실험을 통하여 본 논문의 제안구조를 사용하면 유압 실린더 내 피스톤 위치측정이 가능함을 확인하였다.

• 한국산업융합학회 논문집
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• 제19권3호
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• pp.160-166
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• 2016

This study proposes the development and performance evaluation of electronic proportional control valve having an LVDT. The electronic proportional control valve is composed of hydraulic valve, proportional solenoid and controller. LVDT is to reduce the steady state error for the reference input of the controller by the feedback signal to detect the displacement of the spool. Designed LVDT is applied to the common proportional valve. In order to evaluate the performance of the developed valve, the hydraulic test equipment was developed and flow tests were carried out. From experimental results, it was proved that the hysteresis was less than 1% based on the maximum flow rate.

• 분석과학
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• 제18권5호
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• pp.410-418
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• 2005

PCBs는 뛰어난 물리 화학적, 열적 안전성과 전기 절연성으로 인해 윤활유, 열교환유체, 복사지 등 많은 용도로 사용되어 왔으며, 1930년대에서 1970년대까지 Aroclors, Kaneclors, Clophens, Phenaclors 등과 같은 상업적 PCBs 생산품들이 절연유로 사용되었다. 본 연구에서는 PCBs의 주된 배출원인 변압기 절연유를 채취하여 Aroclor 1242, 1248, 1254, 1260의 표준물질을 사용하여 정성분석을 하였다. 제작년도 및 제작사별로 채취 분석한 결과 절연유는 Aroclor 1242, Aroclor 1254, Aroclor 1260의 단일 제품을 함유하거나 이들이 혼합되어 함유되어 있는 것으로 조사되었다. 또한, 시판되는 스크리닝 키트(20 ppm, 50 ppm)를 이용한 절연유 시료 분석방법의 적용성을 검토하였다.

• 조명전기설비학회논문지
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• 제15권5호
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• pp.97-107
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• 2001

화력발전소, 수력발전소, 그리고 펄프 및 제지 산업분야 발전 프랜트들은 노후화된 발전기 여자시스템으로 인해서 많은 보수 정비업무에 직면해 있다. 이러한 노후 발전설비의 수명 연장을 위해 한전 전력연구원 3중화 디지털 정지형 여자시스템을 개발하였다. 이 논문에서는 3중화 정지형 여자시스템을 구성하는 전력전자 제어 소자(싸이리스터, GTO), 여자 변압기, 3중화 제어시스템의 설계개념과 현장 적용 결과에 대해서 기술하고자 한다.

• 산업기술연구
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• 제14권
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• pp.89-100
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• 1994

The effects of transient inrush currents on the dynamic characteristics of percentage differential relays are studied when the power transformers are reenergized. An algorithm of estimation the nonlinear magnetic property of power transformer and current trnasformer core are developed. Using this method, we can analyze the effect of inrush currents on the trip region of the percentage differential relays corresponding to the variation of the phase angle and the residual magnetism at the instant of switch closing. Test results are used to verify the availibility of the proposed algorithm. Finally a case study is performed to the 110 MVA main transformer in hydraulic power station.