• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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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.

• Proceedings of the KSME Conference
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• 2008.11a
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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.

• Proceedings of the KSME Conference
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• 2007.05a
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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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.509-512
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• 2015

In this paper, several capacitive sensors for measuring the position of the piston in hydraulic cylinder was studied and designed. The inductive LVDT sensor has been widely used to measure the position of the piston because of its high accuracy, but this type of sensor is very expensive and has difficulty in use because of its complexity. To overcome these disadvantages, we studied the optimized non-contact capacitive sensors and designed several capacitive sensors for accurate measuring the location of piston in hydraulic cylinder. The proposed capacitive sensor has the possibility of practical use for hydraulic cylinder through experiments.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.3
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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.

• Analytical Science and Technology
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• v.18 no.5
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• pp.410-418
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• 2005

PCBs had numerous uses such as hydraulic fluid, heat exchange fluid, sealant, lubricant, and carbonless copy paper. They are most likely found in electric utilities, power stations, industrial facilities, electronic manufacturing plants, petrochemical plants, railroad systems, electric equipment repair facilities, mining sites (active or abandoned), and military camps. Due to its outstanding chemical and thermal stabilities and electrical insulation properties, the commercial and industrial products of PCBs, such as Aroclors, Kaneclors, Clophens, Phenaclors etc., had been widely used as thermal oil and transformer oil from 1930s until the 1970s. The transformer oils were analyzed as a main source of polychlorinated biphenyls (PCBs) emission into the environment. Qualitative estimation of oil extracts as carried out with Aroclor 1242, 1248, 1254, 1260. The transformer oils contained the pure and mixed of Aroclor 1242, Aroclor 1254, and Aroclor 1260. Also, commercial screening kit of 20 ppm and 50 ppm were applied to the transformer oil samples.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.5
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• pp.97-107
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• 2001

Many power plants in the thermal and hydraulic utilities, the pulp and the paper industry are faced with high maintenance and down time due to the aged excitation system. For the life extension of the aged power plants, the static excitation system of triple module redundancy type had been developed by KEPRI(Korea Electric Power Research Institute). This paper will discuss the design conception and the application results of system which includes the power control devices(thyristors, GTO), power potential transformer(excitation transformer) and triple module redundancy controller(voltage regulator).

• Journal of Industrial Technology
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• v.14
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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.