• Proceedings of the KIEE Conference
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• 2004.07e
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• pp.10-13
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• 2004

The recent growth in the use of impactive and nonlinear loads, electronic devices sensitive to power quality has caused many power quality problems. Dynamic voltage restorers(DVR) are known as the best effective and economic means to compensate for power quality problems(especially, voltage sag and sewll). In this paper, we adresses the detecting algorithsms and implementation techniques of an voltage sag for operating DVR.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1302-1308
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• 2002

Thermo-mechanical and flexural behavior of a wire-bond plastic ball grid array (WB-PBGA) package are characterized by high sensitive moire interferometry. Moire fringe patterns are recorded and analyzed for several bending loads and temperatures. At the temperature higher than $100^{\circ}C$, the inelastic deformation in solder balls become more dominant, so that the bending of the molding compound decreases while temperature increases. The deformation caused by thermally induced bending is compared with that caused by mechanical bending. The strain results show that the solder ball located at the edge of the chip has largest shear strain by the thermal load while the maximum average shear strain by the bending moment occurs in the end solder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.724-728
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• 1996

The instrumented Charpy impact test is generally used to evaluate the dynamic fracture toughness for varying engineering materials. However, the test is known to be difficult to evaluate the dynamic fracture toughness for very brittle materials because of the small crack initiation load. To evaluate the dynamic fracture toughness of verybrittle materials, it is necessary to develop a load sensitive instrumented tup. In this study, a polymer tup, which has small Young's modulus, is used for the instrumented Charpyimpact test and a proper testing method is developed. The results show that the developed method can measure rapidly changing loads from the moment of contact between the tup and the specimen to dynamic crack initation of the very brittle materials.

• Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.1-7
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• 2013

Launch vehicles cause several shock events during their lift-off. The excessive shock loads in the several thousands of g's level can results in permanent damage to electronics, optics and other sensitive payload components. The shock can be attenuated by mounting a shock absorber. In this paper, we proposed a semi-active control logic to attenuate the shock so that the input acceleration to main instruments does not exceed the allowable maximum acceleration value. For the performance investigation, two elements model of variable damping and spring stiffness has been used and the analysis results indicate that the proposed semi-active control logic attenuates shock level better than an optimal passive and conventional semi-active on-off control system.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.164-166
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• 1997

This paper analyze customers' effect caused by momentary voltage variation. Momentary voltage variation is due to a serious results like shutdown of sensitive loads such as electronic equipment, computer, and magnetic contactor. However, conventional reliability ignored the effect of momentary voltage variation. In this paper we analyze the present state of momentary voltage variation in customers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.11
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• pp.84-93
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• 2009

In this paper, we propose to study the possibility of using a photovoltaic system combined with a high speed micro-turbine. This hybrid system can work as stand-alone system or grid connected system as it will be a part of a micro-grid. Initially, we propose Matlab/Simulink dynamic models of photovoltaic, micro turbine systems and supercapacitor. Then, we carry out a simulation comparison of the two systems, this is, with supercapacitor and without supercapacitor bank. We show that supercapacitor bank as short-term storage device was necessary to reduce the fast fluctuation of power in the case of sensitive loads. It is verified the simulation results of Matlab/Simulink based hybrid power system represent the effectiveness of the suggested hybrid power system.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.1018-1023
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• 1998

This paper presents an effective control scheme incorporated in the voltage-fed half-bridge series resonant inverter for induction heating applications, which is based upon a load-adaptive tuned frequency tracking control strategy using PLL(Phase Locked Loop) and its peripheral control circuit. The proposed control strategy ensures a stable operation characteristics of overall inverter system and ZVS(Zero Voltage Switching0 operation in spite of sensitive load parameters variation as well as power regulation, specially in the non-magnetic heating loads. The simulation results and the performance characteristics in the steady-state are shown as compared with the experimental results for a prototype induction cooking system rated at 1.2kW.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.598-602
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• 2002

This paper presents the 3-phase hybrid series active power filter with dynamic voltage restorer(DVR) which serve as an energy buffer and current harmonics blocking resistor connected to sensitive loads, such as, to compensate voltage dips and current harmonics in power distribution system. The DVR is to inject a dynamically controlled voltage generated by a forced commutated converter in series to the bus voltage by means of a booster transformer. The momentary amplitudes of the three injected phase voltages are controlled such as to eliminate any detrimental effects of a bus fault to the load voltage. The proposed system is able to simultaneously compensate current harmonics, voltage fluctuating and voltage unbalance in power distribution systems. The reference phase angle detected by synchronized with the positive sequence component of the unbalanced source by using symmetrical component transformation. The effectiveness of proposed system is verified by the computer simulation.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.374-381
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• 2005

The ability to provide quality power has become a significant issue in power systems. The main causes of poor power quality are harmonic currents, poor power factor, supply-voltage variations, etc. A technique of achieving both active current distortion compensation, power factor correction and also mitigating the supply-voltage variation (sag or swell) at the load side is presented in this paper. The operation and rating issues of the proposed Single-phase Unified Power Quality Conditioner are also highlighted. To reduce the total cost while simultaneously increasing the performance, the system is fully digitally controlled using the fixed-point TMS320F240 digital signal processor. The performances of the UPQC, which is composed by shunt and series PWM controlled-converters, have been verified on a laboratory prototype.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.105-111
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• 2003

The valve train system of engines has long been a sensitive area with respect to wear performance because of the high contact loads and surface sliding speeds encountered. In particular, wear problems of load-carrying components in relative motion, such as cam and tappet in valve train system have made troubles. To overcome these problems, combination of proper materials is important, as well as selecting of high wear performance materials. This paper presents the experimental result of friction and wear properties of ca/tappet materials. To investigate friction and wear properties for several combinations of materials, using commonplace tribometer(Plint 77, reciprocating type), we make a selection of a optimum material combination.