• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.449-451
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• 2001

This study presents a study on modified algorithm to operating train simulation of AT feeding systems. In this study equivalent impedance is constructed by $Z_c,\;Z_r,\;Z_f,\;Z_{cr},\;Z_{rf},\;Z_{fc}$. The train current flows through the all auto-transformer corresponding to track impedance. To calculate train voltage from analyzing the railway systems, the algorithm is based on the K. C. L, K. V. L, superposition and circuit separation method. Multi-train's voltages are determined by calculating the catenary voltage at each train's position and adding up these train's voltage drop. Case studies use a field operational data, show that the proposed method is easily applied.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1402-1404
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• 2000

The electrified railway has various power supply schemes. Although the identical trains are operated in same condition and the impedance of track are equal, the genealogy impedance of track is changed according to composition method of feeding scheme. So, the harmonic current flowing into the railway substation are greatly unlike. For simulation of harmonic magnification flowing into the railway substation according to feeding scheme, we propose 6-port network analysis method based on 4-port network, find 6-port equivalent model of each circuit component, and compare and investigate harmonic magnification in the case of parallel post and normal feeding scheme.

• The Journal of the Acoustical Society of Korea
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• 제26권1E호
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• pp.14-20
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• 2007

The characteristics of a PZT transducer with a cylindrical rear surface were investigated theoretically and experimentally. The transducer was assumed as a set of finite rectangular ceramic elements for applying the staircase model to the theoretical analysis and the KLM equivalent circuit model was modified for analyzing its electric impedance and pulse-echo response. All results were compared with those of a conventional plane transducer which has a constant thickness of average value for the cylindrical arc. It was noted that the transducer with a cylindrical rear surface has several subsidiary resonant frequencies which are able to widen bandwidth.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.273-277
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• 1999

A cold cathode flourescent lamp for the backlight in the notebook computer requires high input voltage about 1300(V) when it turns on. But once a discharge starts, the input voltage can be dropped by about one-third for continued output. The equivalent impedance also varies from open to several dozens of kilo-ohms. The piezoelectric transformer converts electrical energy into mechanical energy and then converts it back to electrical energy at a high voltage. Its high output voltage, high efficiency and small size are suitable for driving the LCD backlight in the notebook computer. The piezoelectric transformer operates near the resonance frequency and the output waveform is close to sine wave with very little noise. This paper suggests an inverter for LCD backlight of notebook computer using piezoelectric transformer that includes voltage to frequency converter for gate signal which is useful for tracking of variable resonance frequency depending on load impedance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.464-468
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• 2003

Complex impedances with frequency and voltage variation were analyzed in $ITO/Alq_3(60nm)/Al$ device structure. At low frequency, complex impedance is mostly expressed by resistive component, and at the high frequency by resistance and capacitive component. We have also evaluated resistance, capacitance and permittivity.

• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.995-999
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• 2007

We investigated the characteristics of a flux-lock type superconducting fault current limiter(SFCL) considering magnetization characteristic of iron core. The flux-lock type SFCL, like other types of SFCLs using the iron core, undergoes the saturation of the iron core during the initial fault time. Therefore, if the design to prevent the saturation of the iron core is considered, the effective fault current limiting operation can be achieved. Through the analysis for its equivalent circuit including the magnetization characteristic of the iron core, the limiting impedance of the flux-lock type SFCL was drawn. The magnetization currents and the limited currents of SFCL, which were dependent on the winding direction and the turns' ratio between two coils, were investigated from the short circuit experiment. It was confirmed that their experimental results agreed with the analysis ones.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.36-38
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• 2018

As the battery capacity requirement increases, battery cells are connected in a parallel configuration. However, the sharing current of each battery cell becomes unequal due to the imbalance between cell's impedance which results the mismatched states of charge (SOC). The conventional fixed-resistance balancing methods have a limitation in battery equalization performance and system efficiency. This paper proposes a battery equalization method based on dynamic resistance technique, which can improve equalization performance and reduce the loss dissipation. Based on the SOC rate of parallel connected battery cells, the switches in the equalization circuit are controlled to change the equivalent series impedance of the parallel branch, which regulates the current flow to maximize SOC utilization. To verify the method, operations of 4 parallel-connected 18650 Li-ion battery cells with 3.7V-2.6Ah individually are simulated on Matlab/Simulink. The results show that the SOCs are balanced within 1% difference with less power dissipation over the conventional method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.613-616
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• 1998

In this paper, a model of a Eddy-current probe coil with a ferrite core in the presence of a half-space with a layer is developed. The half-space with a layer is accounted for by computing the appropriate Green's function by using Bessel transforms. Upon introducing equivalent Amperian currents within a core to explain effect to a impedance change in the coil due to a (ferrite) core, we derive a volume integral equation, The integral equation is transformed via the method of moments into a vector-matrix equation, which is then solved using a linear equation solver. Through the above processing, we computed impedance value in a Eddy-current probe coil due to a conductivity change of layer.

• 한국전자파학회논문지
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• 제14권7호
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• pp.750-755
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• 2003

본 논문에서는 새로운 형태의 3-라인 발룬을 제안하였다. 먼저 3-라인 발룬의 등가회로를 제시하였고, 이등가회로의 각 포트에서의 전압과 전류의 관계를 이용하여 임피던스 행렬,［Z］를 구하고 이를［S］파라미터로 변환하여 제시하였다.［S］파라미터를 이용하여, 제시한 등가회로가 발룬으로 동작할 수 있도록 하는 설계식을 도출하였다 본 논문에서 제안한 등가회로와 설계식의 타당성 및 유용성을 검증하고자 2.4 GHz ISM 대역에서 동작하는 MLC(Multi-layer Ceramic) 칩 발룬을 설계하였고, LTCC(Low Temperature Co-fired Ceramic) 기술을 이용하여 제작하였다. 새로운 3-라인 발룬의 등가회로와 LTCC 기술을 이용한 다층구조를 동시에 적용함으로써 2012사이즈의 초소형 발룬을 구현할 수 있었다. 제작된 발룬의 측정 결과는 3차원 전자장 시뮬레이션 결과 와 매우 유사하였고, 넓은 대역에서 매우 우수한 위상 및 진폭 평형 특성을 보였다. 본 논문에서 제안한 3 라인 발룬은 본 논문에서 보인 것처럼 LTCC 기술을 이용하여 매우 쉽게 구현이 가능할 뿐만 아니라 인쇄회로기판 상의 마이크로 스트립라인 등을 이용하여도 구현이 가능하며 작은 사이즈의 우수한 특성을 가진 발룬이 요구되는 무선랜이나 블루투스 등의 무선 통신 시스템 등에 매우 유용하게 적용될 수 있다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.205-215
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• 2015

Common mode (CM) conducted interference are predicted and compared with experiments in a motor drive system of Electric vehicles in this study. The prediction model considers each part as an equivalent circuit model which is represented by lumped parameters and proposes the parameter extraction method. For the modeling of the inverter, a concentrated and equivalent method is used to process synthetically the CM interference source and the stray capacitance. For the parameter extraction in the power line model, a computation method that combines analytical method and finite element method is used. The modeling of the motor is based on measured date of the impedance and vector fitting technique. It is shown that the parasitic currents and interference voltage in the system can be simulated in the different parts of the prediction model in the conducted frequency range (150 kHz-30 MHz). Experiments have successfully confirmed that the approach is effective.