• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.886-890
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• 2003

This paper introduces the combined test results of the traction system for KHST(Korean High Speed Train: hereafter refer to KHST). The main purpose of this combined test is to verify the performance of the traction system that is designed to operate up to maximum 350km/h speed. Combined test system consists of a traction transformer, two AC-DC PWM converters, a PWM Inverter, two traction motors and flywheel system. Flywheel system represents equivalent model of the train inertia. Also traction control system and MASCON Interfaces are included. Various kinds of experiments are performed to prove total traction system performance and detail waveforms are described

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.33-35
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• 1999

This paper describes the test results of the single phase 3kVA high temperature superconducting power trans-former. The tapes are made with Bi-2223 and have silver alloy as the matrix. Four double pancake windings are used in total. Among them two double pancake windings are connected in series for high voltage winding and two double pancake windings are connected in parallel for low voltage winding. The rated voltages of each winding are 220/110 V. Fundamental characteristics are obtained through short circuit and no load tests. The over load capability and characteristics are investigated.

• 전자공학회논문지B
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• 제33B권10호
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• pp.139-147
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• 1996

In this study a two-stage fast pulse generaor using magnetic switches is proposed. The scheme consist of a switch, an inductor and two pairs of capacitor and saturable inductors, a linear transformer. The basic principle and the operation are described using a set of given parameters. The main issue of the magnetic pulse genration scheme is the system efficiency. This study focuses on the system efficiency improvement using magnetic switches. The voltage compression ratio, energy transfer with respect to core area are investigated. The output voltage and transferred energy as a function of input voltage are also included. Also, an analysis and experiments are performed to verify the porposed topology by implementing a 10[J] class experimental circuit. The efficiency of the transferred energy a tload side is 82%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1354-1356
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• 2000

This paper deals with a 300kV dc charging system to be used ?s a voltage source in a circuit breaker synthetic short-circuit-test facility. Cockcroft-walton circuit is used to step up the rectified voltage from a single phase transformer of which primary winding is hooked up to an ac220 wall plug. Two systems with the same ratings have been designed and manufactured. The two system have been made of different supporting structure with different insulating materials. The paper describes a couple of charging schemes, system configurations and the synthetic test circuit in which the developed system is to be used.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.603-605
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• 1995

This paper introduces aspects of electrical power system with regard to the application of generator circuit breaker(GCB) in nuclear power generating stations. Technical analyses are performed for the two(2) alternatives, one(1) stand-by auxiliary transformer(SAT) vs two(2) SAT's, on system configuration in case that one(1) GCB is used. The results show that one(1) SAT system may not be justified when larger auxiliary loads are required to increase plant availibility. This paper also presents the feasibility on reliability, operability and maintainability for adopting GCB.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2003년도 추계학술대회 발표 논문집
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• pp.182-185
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• 2003

We have suggested an equivalent circuit model for switching performance of bipolar spin transistor composed of a nonmagnetic metal film (N) sandwiched between two ferromagnetic metal films (F1 and F2). The 'ON' or 'OFF' operation of this equivalent circuit model is simulated by depending on the orientation of the magnetization of F1 and F2 rather than the strength of the external magnetic filed. Changing the coupling coefficient, turn number of two inductances, (L1:L2) like a transformer, and parallel variable resistance R4 connected to L2 at the collector region, we can explain the magnetic characteristics and the dependence of magneto resistance ratio on the orientation of spin-polarized electrons.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.156-160
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• 2009

This paper presents the interleaved active-clamping ZVS(Zero Voltage Switching) forward converter, which is mainly composed of two active-clamping forward converters. Only two switches are required, and each one is the auxiliary switch for the other. The circuit complexity and cost are thus reduced. The leakage inductance of the transformer or an additional resonant inductance is employed to achieve ZVS during the dead times. The duty cycles are not limited to be equal and within 50%. The complementary switching and the resulted interleaved output inductor currents diminish the current ripple in output capacitors. Accordingly, the smaller output chokes and capacitors lower the converter volume and increase the power density. Detailed analysis and design of this new interleaved active-clamping forward converter are described.

• 한국안전학회지
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• 제20권3호
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• pp.47-52
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• 2005

Recently, power conversion equipment increased rapidly makes a lot of harmonics. Thus, it is growing that wrong operation and break down of sensitive devices. There are two kinds of causes of harmonics. One of them is lots of power conversion equipment as modem controller, inverter, converter and SWS(Switching Mode Power Supply). Another is nonlinear operating machines as transformer and motor. The more nonlinear loads like them grow, the more serious problems as harmonic current to source and low power factor because of increasing reactive power grow. It is installed for reactor and L-C Filter to decrease harmonic in general. This paper analysis and compares two of characteristics and harmonic from reactor and L-C Filter with operation of induction motor and power conversion equipment. In the result, L-C Filter more improves unbalance rate and THD than reactor.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.45-46
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• 2014

This paper presents a three-phase high-power-density bidirectional DC-DC converter. The converter employs dual three-phase active bridges and a three-phase transformer. The presented converter is controlled by two symmetric PWM modules and phase between two symmetric PWM modules to control the power flow. Simulation is included to verify the presented converter.

• 전자통신동향분석
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• 제37권1호
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• pp.53-62
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• 2022

With increasing size of transformer-based neural networks, a light-weight algorithm and efficient AI accelerator has been developed to train these huge networks in practical design time. In this article, we present a survey of state-of-the-art research on the low-precision computational algorithms especially for floating-point formats and their hardware accelerator. We describe the trends by focusing on the work of two leading research groups-IBM and Seoul National University-which have deep knowledge in both AI algorithm and hardware architecture. For the low-precision algorithm, we summarize two efficient floating-point formats (hybrid FP8 and radix-4 FP4) with accuracy-preserving algorithms for training on the main research stream. Moreover, we describe the AI processor architecture supporting the low-bit mixed precision computing unit including the integer engine.