• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.189-189
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• 2010

The Improved flux-lock type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO coated conductor. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO coated conductor was connected with secondary coil in parallel. In a normal condition, the flux generated from a primary coil is cancelled out by its structure and the zero resistance of the YBCO thin films. When a fault occurs, the resistance of the YBCO coated conductor was generated and the fault current was limited by the SFCL. In this paper, we investigated the fault current limiting characteristics through the spot at the beginning of the fault current in the Improved flux-lock type SFCL. The experiment results that the fault current limiting characteristics was difference according to the point of a fault current started. Through the analysis, it was shown that shorter the time of a phase transition.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.218-225
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• 2010

This paper deals with a method to minimize the welding time for an AC spot welding system. The spot welding system using a conventional SCR type circuit has a disadvantage of slow control speed and no precise current control. Therefore, recently, the using of inverter type welding system is increasing. Conventional welding machine adopts several tens of switching devices connected in parallel to obtain a huge current of several thousands ampere with a short welding time. This paper analyzed a welding system consisting with 4 IGBT switches for a full-bridge inverter and conventional 60 [Hz] transformer. The simulation and experimental results show the validity of the proposed method.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1083-1095
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• 2023

Recently, the demand for low-voltage, high-capacity ESS is rapidly increasing due to the revitalization of the e-mobility industry, which is mainly powered by electricity. In addition, the demand for portable power banks is rapidly increasing due to the revitalization of leisure industries such as camping and fishing. The ESS with this structure consists of a small number of series cells and many parallel cells, resulting in a system with a large rated current. Therefore, the number of power devices for cell balancing configured in series is small, but a balancing device with a large current capacity is required. Construction of a constant temperature device in such a low-voltage, high-current ESS is difficult due to economic issues. The demand for an active balancing system that can solve the passive balancing heating problem is rapidly increasing. In this paper, propose a power feedback fly-back topology that can solve the balancing heating problem. The characteristic of the proposed topology is that a series-connected voltage sharing voltage is used as the input of the flyback converter, and the converter output is connected to one transformer. In this structure, the converter output for cell voltage balancing shares magnetic flux through one high-frequency transformer, so the cell voltage connected to the converter automatically converges to the same voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.131-141
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• 2007

This paper proposes analysis on new equipment for power quality in electric railway. The proposed equipment consists of series inverter and parallel inverter. Each inverter is connected by capacitor as dc link. This structure can be compensated for active and reactive power in catenary through transformer. We verified the proposed equipment using the PSCAD/EMTDC and the calculation results from the proposed approach are widely described in the paper.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.55-64
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• 2007

This paper represents characteristics and design example of series loaded LCC type high frequency resonant DC-DC converter with variable parallel capacitor in the secondary side of inductive power transformer. In this converter, ZVS(zero voltage switching) technique is applied to reduce turn-off switching losses, and the applied converter used the PFM switching pattern to control output voltage. The operating characteristics of the proposed converter is analyzed using nomalized parameter such as switching frequency and load factor with varing the secondary parallel resonant capacitor. The results of analysis show the operating characteristics and design method of the proposed converter using characteristic values. And the proposed converter can be applied for the contactless power supply with linear transfer system such as dean room facilities of semiconductor and Flat Panel Display.

• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.63-70
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• 2023

In this work, a capacitive wireless power transfer (C-WPT) system is presented for wireless sensor system (WSS) applications in marine propulsion shafts. For a single Q factor on both sides of the coupling capacitor and reactive power removal from the circuit, a double-sided LCLC converter and transformers topology are designed to drive the rotary C-WPT system for WSS on the shaft. Parallel-connected parallel plate rotating capacitors with a capacitance of 170 pF are designed and implemented for the C-WPT system on a snow rotating shaft. In the experimental results, the C-WPT system achieved a transmission efficiency of 66.67% with 7.8 W output power at 3 mm distance and 1 MHz operating frequency. Therefore, it was proved that the fabricated C-WPT system can supply power to the WSS of the rotating shaft.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.200-202
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• 2006

We investigated the operating characteristics of a flux-lock type superconducting fault current limiters according to the number of the serial connection each the superconducting element at the additive polarity winding of a transformer. This SFCL consists of two coils wound in parallel on the same iron core, and the secondary coil is connected to the elements in series. Operating characteristics can be controlled by adjusting the inductances and the winding directions of the coils. It turns ratio between the primary and the secondary coils is 63:21. The analysis of voltage, current, and resistance in serial connection each element was performed to increase the applied voltage of flux-lock type SFCL. When the applied voltage was 200/$\sqrt{3}[V_{rms}]$ with three elements connected in seres, the peak value of the line current increased up to 26,24[A]. On the other hands, resistive SFCL increased up to 36.35[A], under the same conditions. This enabled the flux-lock type SFCL to be easy to increase the capacity of power system.

• Journal of Electrical Engineering and Technology
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• v.6 no.6
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• pp.842-848
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• 2011

The current study proposes the design of a hybrid series-parallel resonant converter (SPRC) and a three-stage Cockcroft-Walton voltage multiplier for precisely adjusting the power generated by a continuous wave (CW) $CO_2$ laser. The design of a hybrid SPRC, called LCC resonant converter, is described, and the fundamental approximation of a high-voltage and high-frequency (HVHF) transformer with a resonant tank is discussed. The results of the current study show that the voltage drop and ripple of a three-stage Cockcroft-Walton voltage multiplier depend on frequency. The power generated by a CW $CO_2$ laser can be precisely adjusted by a variable-frequency controller using a DSP (TMS320F2812) microprocessor. The proposed LCC converter could be used to obtain a maximum laser output power of 23 W. Moreover, it could precisely adjust the laser output power within 4.3 to 23 W at an operating frequency range of 187.5 to 370 kHz. The maximum efficiency of the $CO_2$ laser system is approximately 16.5%, and the minimum ripple of output voltage is about 1.62%.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.3
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• pp.26-31
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• 2014

High temperature fuel cell system, such as molten carbonate fuel cells(MCFC) and solid oxide fuel cells(SOFC), are capable of operating at MW rated power output. The power output change of high temperature fuel cell imposes the thermal and mechanical stresses on the fuel cell stack. To minimize the thermal-mechanical stresses on the stack and increase the systems reliability, we should divide the power plant configuration to several banks. However, the improvement of reliability in fuel cell power plant system causes an increase of the investment cost, for example, replacement costs, labor costs, and so on. For this reason - the balance between investment and reliability improvement - many studies about the appropriate level of investment have been conducted. In this paper, we evaluate the cost for operation and installation, the benefit for electric energy and thermal energy sales, and the system reliability for several cases : these cases relate with the bank configuration.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.8
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• pp.329-333
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• 2006

We investigated the quench characteristics of a flux-lock type superconducting fault current limiter (SFCL) depending on the number of the serial connection between the superconducting elements at the subtractive polarity winding of a transformer. The flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil through an iron core, and the secondary coil is connected to the superconducting elements in series. The operation of the flux-lock type SFCL can be divided into the subtractive and the additive polarity windings depending on the winding directions between the primary and secondary coils. In this paper, the analyses of voltage, current, and resistance of superconducting elements in serial connection were performed to increase the power capacity of flux-lock type SFCL. The power burden was reduced through the simultaneous quenching between the superconducting elements. This enabled the flux-lock type SFCL to be easy to increase the capacity of power system.