• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.35-38
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• 2000

A preliminary design of gas-gp thermal switch is presented to reduce the cooldown time of superconducting system conduction-cooled by a two-stage refrigerator without liquid cryogens. The switch connects thermally the first and the second stages (ON) to take advantage of the larger refrigeration capacity at the first stage during the beginning period. After the cryogenic temperature is reached, the switch should isolate thermally the two stages (OFF) in order to reduce the heat leak to the cold end. In this paper, a new concept for the performance index is introduced to evaluate the reduction of the cooldown time and the increase of the cooling load at the same time. In addition, the design of a gas-gap switch is discussed as a closed container of several staggered concentric tubes filled with gas, which is frozen at low temperatures for the shut-off of heat without any mechanical actuation. Some of the detailed features in the design is quantitative investigated by the gas convection model in the continuum or the rarefied gas region.

• Journal of Power Electronics
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• 제14권1호
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• pp.1-10
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• 2014

This paper proposes a high-efficiency supercapacitor charger. Conventional two-switch forward converter can be used for charging supercapacitors. However, the efficiency of conventional converters is low because of their switching losses. This study presents a high-efficiency two-switch forward converter for supercapacitor chargers. The proposed converter improves power efficiency by 4 %, from 89 % to 93 %. The proposed converter has the advantages of reduced switch voltage stresses and minimized circulating current when compared to other converter topologies. The performance of the proposed converter is evaluated by experimental results using a 300 W prototype circuit for a 54-V, 35-F supercapacitor bank.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.252-257
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• 1998

Two-stage power factor correction (PFC) converter with a single PWM controller for universal input voltage (90-264V) is proposed. It consists of a power factor pre-regulator cascaded by a DC/DC converter as in a conventional two-stage approach. However, a single PWM controller is used as in a single-stage, single-switch PFC approach. The switch in the PFC part is synchronized with the switch in the DC/DC converter with a fixed switching frequency. Employing an adaptive delay scheme the switch in the PFC part is controlled to limit the energy storage capacitor voltage within a designed range for the optimum efficiency, and to reduce input current harmonic distortion. The experimental results obtained on a 200W (5V/40A) prototype PFC converter are given to verify the effectiveness of the proposed control method.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.196-199
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• 2003

Characteristics of a heater-triggered switch has been analyzed through the simulations and experiments. It was for the charging of Bi-2223 double pancake load with 1.7 mH and two heaters were used. The timing of the sequential control and the heating current with two heaters are important factors to generate pumping-current. The thermal analysis of the switch considering the heater input and time was carried out. Based on the analysis just mentioned. heater-triggered switch was fabricated. Characteristic analysis was carried out through two modes having different sequential timing controls. Maximum pumping-current reached 18 A and the pumping rate was 113 mA/s at that time.

• 소성∙가공
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• 제4권1호
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• pp.17-27
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• 1995

The tact switch is widely used in electric and electronic products. The dome type tact spring is produced by stamping. Stamping of the tact spring and operation of the tact switch have been simulated by the elasto-plastic finite element method. The operating characteristics of the switch may be given by the relation between the operating force and stroke. For a given material, this is affected by two main factors. One is the geometry of dome spring which is determined by the geometry of stamping dies and the stamping pressure, and another one is the dimension of switch. From the calculation, it was possible to obtain the stamping conditions and switch dimension for a predetermined force-stroki relation And, the hoop stresses and effective strains distributions due to the stamping and during the operation of the switch indicate a possibility of cracking in the center and rim of dome spring.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.155-157
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• 2009

This paper proposed a soft switching boost converter with an auxiliary circuit, and a modified control method for reduction of switch stress. The proposed converter applies an auxiliary circuit, which is added to the conventional boost converter and used to achieve soft switching for both a main switch and an auxiliary switch. The auxiliary circuit consist of a resonant inductor and two capacitors, an auxiliary switch. The main switch is operated ZVS turn-on, turn-off also auxiliary switch is operated ZCS turn-on, ZVS turn-off. The proposed soft switching boost converter has lower switch loss and higher efficiency than conventional soft switching boost converter.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.23-28
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• 2007

In this paper, we propose ATM switch structure including AAL type 2 switch which can efficiently transmit low-bit rate data, even if the network has many endpoints. We simulate the architecture of ATM switch fabric that is modeled in computer program and analyze the performance according to offered loads. ATM switch proposed in this paper can support cell switching for all types of AAL cells which consist of AAL type 1, AAL type 2, AAL type 3/4, and AAL type 5 cells. We propose two switch fabric methods; One supports the AAL type 2 cell processing per input port, the other global AAL type 2 cell processing for every input port. The simulation results show that the latter is superior to the former. But the former has a strong point for easy implementation and extensibility. The proposed ATM switch fabric architecture is applicable to mobile communication, narrow band services over ATM network.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 B
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• pp.594-596
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• 1998

In this paper, a path control switch has been developed for self-healing operation in SDH-based transmission system. The proposed switch is suitable for self-healing operations in both an Unidirectional Path Switched Ring and a 2-fiber Bidirectional Line Switched Ring. The path control switch is implemented with $0.8{\mu}m$ CMOS LSI chip. The self-healing operation of the switch is effectively done by the configuration information stored in the registers of the switch. The switch has an AU-3(51.84Mb/s) TSI(Time Slot Interchange) and has 1.25Gb/s throughput. But the higher throughput can be realized by combining two identical switches or more with the parallel architecture.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권1호
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• pp.19-24
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• 2003

Design and test results of a VRAG(Vacuum Rotary Arc Gap) switch were presented. To control the damage of electrodes caused by the vacuum arc, Lorentz's force by the radial magnetic field between spiral electrodes was used to rotate the vacuum uc. VRAG switch electrodes were made of the material of CuCr and OFHC. Gap distance between two spiral type electrodes for the rotation of the arc discharge is 8, 10, 12mm. In the cathode, one trigger electrode was inserted into each spiral wing. Normal operation of the VRAG switch was confirmed with 10.6[$mutextrm{s}$]of trigger delay and 2~3[$mutextrm{s}$] of the jitter time. The speed of the vacuum arc was measured to be 0.6 ~ 1[km/s] by a motion analyzer.

• Journal of Magnetics
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• 제18권1호
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• pp.50-56
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• 2013

In this paper, the 6-switch inverter for the Flux-Reversal Motor (FRM) has been presented and compared to the 4-switch inverter for the FRM, which is more popular in cost effective applications. To analyze the FRM, we adopted the two-dimensional time-stepped voltage source finite element method (FEM) that uses the actual pulse width modulation (PWM) voltage waveforms as the input data. As the FRM characteristic analysis of actual pwm voltage input, the torque ripples and iron losses (eddy current and hysteresis loss) of the FRM can be precisely calculated. With the simulated and experimental results, the performance and limitations of the 4-switch FRM which is the cost effective drive compared to the 6-switch FRM drive are provided in more detail.