• Journal of Institute of Convergence Technology
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• v.3 no.1
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• pp.19-23
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• 2013

This study is concerned with air-conditioning system in use of thermoelectric device. It is introduced that the well designed structures for better cooling & heating performance with high efficiency. And also it is performed that the system performance test of four types trial products for the use of hybrid commercial vehicle. System performance is affected by many component parts, especially heat sink design & power control method. It is applied that dual extrusive fin tube with buffer zone for the effective radiating of circulating liquid in tube. And also it is applied that power supply method with constant-current system. It is attained that system cooling capacity is 1.2kW, COP is 0.95.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.466-468
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• 2002

In order to newly define and specify the performance and the testing method of the high-voltage circuit breaker, IEC 62271-100 was published in May, 2001 and took place of IEC 60056 which had been used since 1987. This new standard intensifies the requirement and the test method of the circuit breaker and also domestic manufacturer makes progress the new product development. And, KERI also goes on the build-up project of short-circuit testing facilities for fulfilling the testing method requirements in new IEC 62271-100. This paper introduce the limiting method of short-circuit making current by controlling the time constant of dc component.

• Journal of Power Electronics
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• v.12 no.2
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• pp.233-241
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• 2012

This paper presents a design of a 30kW 250V/530V bidirectional DC-DC converter to be used in an electrical car. A detailed explanation of the design is given. The system uses two phase shifted half bridge (boost and buck) topologies to reduce the ripple current in the output capacitor. The converter has an efficiency of 95% at nominal power. It works as a constant voltage in one direction and as a constant current in the other to charge the batteries. Simulations and measurement are done at high power to test the efficiency.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.42-48
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• 2011

440A martensitic stainless steels which were modified with reduced carbon content(~0.5%) and addition of small amount of nickel, vanadium, tungsten and molybdenum were manufactured. Effects of alloying elements and tempering temperatures on the uniform corrosion in the solution of lN H2S04 were investigated through the electrochemical polarization test. When tempering temperature is constant, corrosion current density in active-passive transition point, Icorr, decreased a little with an increase of austenitizing temperature. In addition to this, when austenitizing temperature is constant, longer holding time showed a little lower Icorr and Ipass, passive current density. And when austenitized at $1050^{\circ}C$ and tempered in a range of $350{\sim}750^{\circ}C$, best anti-corrosion properties were obtained at $350^{\circ}C$ tempering temperature while worst at $450^{\circ}C$ or $550^{\circ}C$. The specimens tempered at below $450^{\circ}C$ and above $550^{\circ}C$, similar and good anti-corrosion characteristics were obtained regardless of alloying elements added, showing anti-corrosion characteristics are influenced more by tempering temperature than by alloying elements.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.240-249
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• 2018

Individual DC voltage balance problem is an inherent issue for cascaded H-bridge (CHB) based converter. When the CHB-based static synchronous compensator (STATCOM) is operating at zero current mode, the software-based individual DC voltage balancing control techniques may not work because of the infinitesimal output current. However, the different power losses of each cell would lead to the individual DC voltages unbalance. The uneven power losses on the local supplied cell-controllers (including the control circuit and drive circuit) would especially cause the divergence of individual DC voltages, due to their characteristic as constant power loads. To solve this problem, this paper proposes an adaptive voltage balancing module which is designed in the cell-controller board with small size and low cost circuits. It is controlled to make the power loss of the cell a constant resistance load, thus the DC voltages are balanced in zero current mode. Field test in a 10kV STATCOM confirms the performance of the proposed method.

• Journal of the Korean institute of surface engineering
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• v.43 no.6
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• pp.283-288
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• 2010

Ni-$TiO_2$ nano composite coatings were fabricated using pulse current electrodeposition technique at 100 Hz pulse frequency with a constant 50% pulse duty cycles and reference was taken with respect to the direct current (dc) electrodeposition. The properties of the composite coatings were investigated by using SEM, XRD, Wear test and Vicker's microhardness test. Pulse electrodeposited composite has exhibited enhancement of (111), (220), and (311) diffraction lines with an attenuation of (200) line. The results demonstrated that the microhardness of composite coatings under pulse condition was significantly improved than that of pure nickel coating as well as dc electrodeposited Ni-$TiO_2$ composite coatings. Wear tracks have shown the less plastic deformation in pulse plated composite. Coefficient of friction was also found to be lower in pulse plated composite coatings as compared to dc plated composite coatings.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.93-100
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• 2011

This paper presents a technical study for the first short stroke lightning current generator using a crowbar device. The so-called crowbar-technology is most common to make 10/350[${\mu}s$] impulse currents with high amplitude, and the lightning current generator with crowbar device has an economic advantage than the nominal RLC current generator. But both the operating efficiency and the operating reliability of crowbar spark gap are very important to design the current generator. So, the peaking circuit which consists of small capacitors and a spark gap is applied. And the multi-step coil for controlling the circuit constant at the different test conditions is used. The presented test facility is designed to perform impulse tests with amplitudes up to 50[kA] of 10/350[${\mu}s$].

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.85-92
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• 2018

In this paper, we designed a 150W LED lighting SMPS circuit operating at $-40^{\circ}C$. We designed a 150W LED lighting constant current circuit for the characteristics of the SMPS and fabricated and measured. The operating temperature range for a 150W LED lighting SMPS circuit is -40 to $70^{\circ}C$ and SMPS predicted life was 1.29-2.25 years based on 24 hours. The high acceleration life test and EMI test confirmed no abnormality.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.258-265
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• 2011

This paper presents a variable frequency current control scheme for the air-pressure control of diaphragm. Differ from the conventional air-pressure control of diaphragm, the proposed method uses a single-phase inverter to control the phase current and frequency. The phase current is adjusted to keep the reference air-pressure of the diaphragm. And the current frequency is changed to reduce the mechanical vibration. In order to smooth change of the operation with a constant air-pressure, the frequency is changed according to the voltage reference from the current controller. When the phase current is satisfied to the constant air-pressure, the current frequency is increased to reduce the vibration of the diaphragm. When the reference voltage to keep the phase current is over than the set value, the current frequency is decreased to keep the air-pressure. The proposed control scheme is verified by the experimental test of a commercial diaphragm.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.48-57
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• 1996

The weldability of high purity aluminum-lithium binary alloys has been investigated using the Varestraint test. Autogenous GTAW (gas-tungsten-arc-welds) were run along specimens of different lithium concentration using three sets of welding parameters. Welding voltage was held constant at 10 volts. Welding current (70∼100 amps) and travel speed (23∼33 cm/min) were the parameter varied. Hot-tearing susceptibility varied with lithium content and exhibited a steep peak at 2.6 weight percent lithium. Depth of penetration increased with increasing heat input and lithium concentration. The susceptibility is influenced by the wettability of dendrites by the interdendritic eutectic liquid as well as the time available for back-Siting by eutectic liquid. The welding condition of welding current 70A and travel speed 23 cm/min was showed good resistance to cracking in aluminum-lithium alloys. Suggestions for improving weld cracking resistance are also provided.