• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.220-223
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• 2003

High-Tc superconducting(HT S) systems are commercialized by many study on high-Tc superconductor. For the successful commercialization of superconducting systems using Bi-2223 wires, the database on the degradation of critical current is essentially needed. In this paper, critical current variation of Bi-2223 wires according to the transport time was investigated. The degradation rate of critical current was also calculated. Solenoid type specimens have the length of 190cm Bi-2223 wire and double-pancake type specimens have the length of l0m wire were tested. Tested Bi-2223 wires are commercialized products of AMSC (American Superconductor) and Innost. When the transportation current was 95% of critical current, the degradation of critical current was appeared after 5 hours of transport time.

• Progress in Superconductivity and Cryogenics
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• v.1 no.1
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• pp.22-27
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• 1999

Recently, small-sized superconducting magnetic storage($\mu$SMES) coils become commercially as an energy storage device for a power conditioner. In design and fabrication of the $\mu$SMES coils, to determine optimum current capacity of the superconducting(SC) conductors is one of the important things. We thus investigated the effect of conductor's current capacity, current density, and stability on the coil's maximum stored energy density in consideration of AC losses and switching device's capacities in a power converter. The results show that the smaller current capacity of the SC conductors is preferred for the $\mu$SMES coils but can increase their induced voltage excessively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.112-115
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• 2011

To stabilize the electric characteristic of Silicon Thin Film Transistor, reducing the current leakage is most important issue. To reduce the current leakage, many ideas were suggested. But the increase of mask layer also increased the cost. On this research Bird's Beak process was use to present element. Using Silvaco simulator, it was proven that it was able to reduce current leakage without mask layer. As a result, it was possible to suggest the structure that can reduce the current leakage to 1.39nA without having mask layer increase. Also, I was able to lead the result that electric characteristic (on/off current ratio) was improved compare from conventional structure.

• Journal of Power Electronics
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• v.1 no.2
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• pp.71-77
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• 2001

This paper proposes a new zero-current switching (ZCS) pulse-width modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero current condition. The diodes commutate softly and the reverse recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of DC to DC PWM converters is derived. The new family of ZCS PWM converters is suitable for the high power applications employing IGBTs. Among the new family of DC to DB PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5 kW prototype converter operating at 40 kHz.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.300-302
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• 1995

This paper describes a current control method for a single-phase PWM inverter. The proposed PWM inverter utilizes the instantaneous control method which is based on the real-time digital feedback control and the microprocessor-based deadbeat control. For the deadbeat current controller, the system's order becomes a high order and increases computation delay time. Therefore, The delay time produces current ripple. To minimize the current ripple, a new method based on deadbeat control theory for current regulation is proposed. It is constructed by a reduced-order state observer which predicts the output current in next sampling instant.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.951-953
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• 2005

The current transformer is used for the insulation of measuring instrument, enlargement of measurement scope, standardization of measuring instrument, control of protective device. It's required various performance as the intention of service, site of establishment, insulation. especailly, current transformer has small ratio errors. if current transformer has large ratio error, it's caused a electricity failure. so in this paper, we examine the theory of current transformer, major factor of errors, output performance on over-current.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.213-220
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• 1999

The purpose of this study is to apply cathodic protection to reinforced concrete structure and provide fundamental data to prevent the corrosion. The theory of cathodic protection of steel in concrete is to apply sufficient direct current so that corroding anodes on the steel are prevented from discharging ions. Two methods are used to supply the external current. In one, the protected metal is the cathode by connecting it to a more active metal. In the second, an external direct current power source supplies the current. The first is the sacrificial-anode system and the second the impressed-current system. The study results showed that the corrosion of the reinforcing steel in concrete could be enormously decreased by using protective current. The sacrificial anode and concrete nave to be adhered closely each in order to prevent the corrosion of reinforcing steel.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.378-386
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• 2014

In this study, the characteristics of the current and wind forces acting on two floating bodies were numerically investigated using a commercial CFD software, STAR-CCM+. In the numerical analyses, LNGC was located right behind FSRU under uniform current or wind conditions. Steady calculations were carried out using a Reynolds averaged Navier-Stokes (RANS) solver and the realized k-epsilon model. First, the current coefficients of FSRU based only the CFD were compared with the model test data. Through this comparison, the present numerical models and mesh systems were indirectly verified. Next, computations for FSRU and LNGC in a uniform current were performed using different relative positions. It was found that the current coefficients were great affected by the longitudinal positions. Finally, the wind forces acting on FSRU and LNGC in tandem configurations were studied. The focus was on the shielding effects due to the aerodynamic interactions between FSRU and LNGC.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.4
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• pp.367-373
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• 2014

The most common current controller for the Switched Reluctance Motor (SRM) is the hysteresis controller. This method, however, suffers from such drawbacks as variable switching frequency, consequent audible noise and high current ripple. These disadvantages make this controlling method undesirable for many applications. The alternative solution is the PI controller. Since the fixed gain PI current controller can only be optimized for one operating point, and on the other hand, SR motor is highly nonlinear, PI controller gain should be adjusted according to incremental inductance. This paper presents a novel method for PI current controller gain adaptation which is simple and yields a good performance. The proposed controller has been implemented on a test bench using a eZdsp F28335 board. The performance of the current controller has been investigated in both simulation and experimental tests using a four-phase 8/6 4KW SRM drive system.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.345-350
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• 2001

Dynamic behavior of high speed train is very important because the high speed train should be safe and satisfied with the ride comfort. An eddy current brake system is mounted on trailer bogie and wheelset. The eddy current braking force longitudinally exerts on the articulated trailer bogie and the attraction force vertically exerts on the wheelset. Because a frame of eddy current brake system is flexible, these forces generate the vertical vibration at middle point of the frame. Also, the vibration change the vertical clearance between an electromagnet and top of rail which affect the magnitude of braking and attracting forces. Therefore, the dynamic behavior of the eddy current braking system must be predicted for design the dynamic characteristic of its mounting system when normally operate on rail which have irregularity. Vampire program is used for prediction of the dynamic behavior of an eddy current braking system. Five design variables and five performance index are considered for optimization through D-optimal experimental design in this paper. Also model center is used to search the optimal point for sum of performance index with variational matric method.