• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권6호
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• pp.322-329
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• 1999

In this paper a practical series-parallel compensated UPS is suggested, which has high input power factor and sinusoidal output voltage regulation capability. Compared to conventional cascaded UPS, the size can be reduced significantly with high quality input and output waveforms. The front converter and the main inverter can be considered decoupled, hence the front converter and the main inverter can be designed independent of each other. In this paper, analysis and experimental results for an l KVA prototype are presented.

• 전력전자학회논문지
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• 제23권1호
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• pp.40-46
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• 2018

In this study, the output voltage balancing characteristics of parallel-input series-output (PISO) boost converter is analyzed. The PISO boost converter is derived by combining two basic boost converters. In comparison with the conventional three-level boost converter, the PISO boost converter can balance the output voltages under an unbalanced load condition without requiring additional circuit components and control strategy. A 2 kW prototype converter is built and tested to verify the output voltage balancing characteristics of the PISO boost converter.

• International Journal of Reliability and Applications
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• 제8권2호
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• pp.137-151
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• 2007

Posbist reliability of typical systems is preliminarily discussed in Cai (1991). In this paper, we focus on the posbist reliability analysis of some typical systems in depth. First, the lifetime of the system is dealt as a fuzzy variable defined on the possibility space (U, ${\phi}$, $P_{oss}$) and the universe of discourse is expanded from (0, $+{\infty}$) to ($-{\infty},\;+{\infty}$). Then, a concrete possibility distribution function of the fuzzy variable is given, i.e., a Gaussian fuzzy variable. Finally, posbist reliability of typical systems (series, parallel, series-parallel, parallel-series, cold redundant system) is deduced. The expansion makes the proofs of some theorems straightforward and allows us to easily obtain the posbist reliability of typical systems. To illustrate the method a numerical example is given.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권2호
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• pp.92-98
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• 2002

It is necessary to measure the solar cell parameter fur understanding characteristic of solar cell and applying to many other fields. Since photovoltaic system consists of solar cell module, which are connected each other in series and parallel, it is not proper to apply a solar cell parameter to photovoltaic system. Therefore, to estimate the solar tell module and to solve the problem of the established algorithm is on demand. In this paper the authors have improved the accuracy of solar cell module Parameter estimation by compensating series and Parallel resistance, and developed a new parameter estimation algorithm, which can be applied to photovoltaic system without high cost measuring equipment. And the validity of proposed algorithm is verified by the simulation and experimentation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1425-1427
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• 2005

In this paper, with loosely coupled transformer series-parallel resonant type DC/DC converter is analyzed. To get more efficient operating mode of the series-parallel resonant type DC/DC converter, theoretical analysis using normalized parameters are accepted. The proposed converter must be operated in Pulse Frequency Modulation(PFM) switching pattern for the Zero Voltage Switching(ZVS) operation. According to PFM control method, the output voltage of the proposed circuit can be controlled.

• 한국산학기술학회논문지
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• 제6권3호
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• pp.278-284
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• 2005

본 논문에서는 통신 기지국용 전원으로 사용할 수 있는 위상 제어 직렬 공진형 컨버터 시스템을 제안하고 동작 원리 및 특성을 살펴보았다. 위상 제어 직렬 공진형 컨버터 시스템은 POSR(Parallel Output Series Resonant) 형태이기 때문에 부하에 강인하고 MOSFET스위치의 위상을 제어함으로써 입력전압의 변화에도 안정된 출력을 보여준다 먼저 시스템의 분석과 PSIM프로그램을 사용한 시뮬레이션을 하였고, 또한 실제 시스템의 실험을 통하여 시스템의 특성을 확인하였다.

• 한국세라믹학회지
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• 제53권1호
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• pp.43-49
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• 2016

This analyzed a Young's modulus (E), a thermal expansion coefficient (TEC, ${\beta}$) and a thermal conductivity (${\kappa}$) of the material with simple cubic particulate inclusion using two model structures: a parallel structure and a series structure of laminated layers. The derived ${\beta}$ equations were applied to calculate the ${\beta}$ value of the W-MgO system. The accuracy was higher for the series model structure than for the parallel model structure. Young's moduli ($E_c$) of sintered porous alumina compacts were theoretically related to the development of neck growth of grain boundary between sintered two particles and expressed as a function of porosity. The series structure model with cubic pores explained well the increased tendency of $E_c$ with neck growth rather than the parallel structure model. The thermal conductivity of the three phase system of alumina-mullite-pore was calculated by a theoretical equation developed in this research group, and compared with the experimental results. The pores in the sintered composite were treated as one phase. The measured thermal conductivity of the composite with 0.5-25% porosity (open and closed pores) was in accordance with the theoretical prediction based on the parallel structure model.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권8호
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• pp.403-407
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• 2006

Standard capacitors, as like as Hamon resistor standards, of series connection/parallel connection ratio $10{\mu}F/1000{\mu}F\;and\;100{\mu}F/10000{\mu}F$ were fabricated for calibration of impedance bridges or analyzers with measuring ranges up to 1 F. The calculated correction terms to the ratio of one measured value in series connection to the value in parallel connection were evaluated to be $1.92{\times}10^{-7}$. These capacitors were designed to be used not only as 100:1 capacitance standards but also as single capacitors or decade capacitors with decade values at frequencies up to 1 kHz.

• Smart Structures and Systems
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• 제25권4호
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• pp.423-432
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• 2020

In this paper, a novel but practical approach named series/parallel multi-sensing technique was proposed to evaluate the bolt looseness in a bolt group. The smart washers (SWs), which were fabricated by embedding a Lead Zirconate Titanate (PZT) transducer into two flat metal rings, were installed to the bolts group. By series connection of SWs, the impedance signals of different bolts can be obtained through only one sweep. Therefore, once the loosening occurred, the shift of different peak frequencies can be used to locate which bolt has loosened. The proposed multi input single output (MISO) damage detection scheme is very suitable for the structural health monitoring (SHM) of joint with a large number of bolts connection. Another notable contribution of this paper is the proposal of 3-dB bandwidth root mean square deviation (3 dB-RMSD) which can quantitatively evaluate the severity of bolt looseness. Compared with the traditional naked-eye observation method, the equivalent circuit based 3-dB bandwidth can accurately define the calculation range of RMSD. An experiment with three bolted connection specimens that installed the SWs was carried out to validate our proposed approach. Experimental result shows that the proposed 3 dB-RMSD based multi-sensing technique can not only identify the loosened bolt but also monitor the severity of bolt looseness.

• Journal of Power Electronics
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• 제12권4호
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• pp.528-537
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• 2012

This paper presents an interleaved resonant converter with a parallel-series transformer connection in order to achieve ripple current reduction at the output capacitor, zero voltage turn-on for the active switches, zero current turn-off for the rectifier diodes, less voltage stress on the rectifier diodes, and less current stress on the transformer primary windings. The primary windings of the two transformers are connected in parallel in order to share the input current and to reduce the root-mean-square (rms) current on the primary windings. The secondary windings of the two transformers are connected in series in order to ensure that the transformer primary currents are balanced. A full-wave diode rectifier is used at the output side to clamp the voltage stress of the rectifier diode at the output voltage. Two circuit modules are operated with the interleaved PWM scheme so that the input and output ripple currents are reduced. Based on the resonant behavior, all of the active switches are turned on under zero voltage switching (ZVS), and the rectifier diodes are turned off under zero current switching (ZCS) if the operating switching frequency is less than the series resonant frequency. Finally, experiments with a 1kW prototype are described to verify the effectiveness of the proposed converter.