• Title/Summary/Keyword: impedance-based method

Search Result 603, Processing Time 0.03 seconds

Evaluation of Corrosion Behavior of Railway Axle Material (RSA1) in Seawater (해수환경에서의 차축소재(RSA1) 부식특성 평가)

  • Choi, Dooho;Seo, Sung-il
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.16 no.8
    • /
    • pp.5039-5044
    • /
    • 2015
  • In this study, we evaluated corrosion behavior of a common rolling stock axle material, RSA1, in seawater. 3-electrode electrochemical cell experiment was conducted using artificial sea water, fabricated according to ASTM-D1141 set by American Society for Testing and Materials, where the corrosion current density and corrosion rate were determined to be $18.3{\mu}A/cm2$ and 0.217 mm/yr, respectively, by employing potentiodynamic test method and impedance spectroscopy method. Considering the fact that life time of railway car is ~25 years, the expected corrosion layer depth is 5mm. Constant-current corrosion test was conducted to accelerate the corrosion process, to reach corrosion periods of 1,3 and 4 years based on Faraday's law, followed by tension tests where the reduced specimen gauge cross-section was re-measured for stress calculation. While no apparent corrosion-related changes in mechanical properties were observed in the elastic regime, the reduction in ductility of the material was found to be increased as the corrosion period increased. The results of this study are expected to be basic corrosion data for the design of rolling stock axles, which will be operated in the sea water environment.

The Implementation of High speed Memory module Interface in the Military Single Board Computer (군용Single Board Computer에서의 고속메모리모듈 I/F구현)

  • Lee, Teuc-Soo;Kim, Young-Kil
    • Journal of the Korea Institute of Information and Communication Engineering
    • /
    • v.15 no.3
    • /
    • pp.521-527
    • /
    • 2011
  • POWER PC series are common to the Central Processing Unit for Military Single Board Computer. Among them, G4 group, which contains the 74xx series supported by Freescale manufacturer is mainly used in the Military applications. We focus on the Interface between memory and controller. PCB stacking method, component routing, impedance matching and harsh environment for Military spec are the main constraints for implementation. Also, we developed memory as a module for the consideration of Military environments. The overall type of SBC should be designed by the form of 6U VME or 3U VME. Therefore this study suggests the electrically optimum Interface matching, Artwork technology based on the signal cross over and PCB stacking method on the harsh environment.

Multiple Model Adaptive Estimation of the SOC of Li-ion battery for HEV/EV (다중모델추정기법을 이용한 HEV/EV용 리튬이온전지의 잔존충전용량 추정)

  • Jung, Hae-Bong;Kim, Young-Chol
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.60 no.1
    • /
    • pp.142-149
    • /
    • 2011
  • This paper presents a new state of charge(SOC) estimation of large capacity of Li-ion battery (LIB) based on the multiple model adaptive estimation(MMAE) method. We first introduce an equivalent circuit model of LIB. The relationship between the terminal voltage and the open circuit voltage(OCV) is nonlinear and may vary depending on the changes of temperature and C-rate. In this paper, such behaviors are described as a set of multiple linear time invariant impedance models. Each model is identified at a temperature and a C-rate. These model set must be obtained a priori for a given LIB. It is shown that most of impedances can be modeled by first-order and second-order transfer functions. For the real time estimation, we transform the continuous time models into difference equations. Subsequently, we construct the model banks in the manner that each bank consists of four adjacent models. When an operating point of cell temperature and current is given, the corresponding model bank is directly determined so that it is included in the interval generated by four operating points of the model bank. The MMAE of SOC at an arbitrary operating point (T $^{\circ}C$, $I_{bat}$[A]) is performed by calculating a linear combination of voltage drops, which are obtained by four models of the selected model bank. The demonstration of the proposed method is shown through simulations using DUALFOIL.

The Design of a Wideband 3 dB Quadrature Coupler using N-Section Parallel-Coupled Lines (N단 평행 결합 선로를 이용한 90° 광대역 3 dB 결합기 설계)

  • 조정훈;윤상원
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.13 no.1
    • /
    • pp.94-100
    • /
    • 2002
  • In this paper, we proposed a 3 dB coupler using N-section parallel-coupled lines and designed a very compact one based on the analysis results. The coupled line has been analyzed by spectral domain method. After we obtain the s-parameters of N-section parallel-coupled lines by using port reduction method 4-port s-parameters are derived. The 3 dB couplers, which were fabricated, are not necessary to implement high impedance lines and tight coupling gaps as Lange Couplers because loose coupling is used. To realize a minimum section, we used the PCB that has high a dielectric constant and a thickness. The experimental results show that it has wide bandwidth of about 42 %(0.5 dB unbalance) from 3.6 GHz to 5.5 GHz and phase difference within 1 degree. Also, The isolation characteristics about 15 dB at its pass-band are obtained.

Research of an On-Line Measurement Method for High-power IGBT Collector Current

  • Hu, Liangdeng;Sun, Chi;Zhao, Zhihua
    • Journal of Power Electronics
    • /
    • v.16 no.1
    • /
    • pp.362-373
    • /
    • 2016
  • The on-line measurement of high-power IGBT collector current is important for the hierarchical control and short-circuit and overcurrent protection of its driver and the sensorless control of the converter. The conventional on-line measurement methods for IGBT collector current are not suitable for engineering measurement due to their large-size, high-cost, low-efficiency sensors, current transformers or dividers, etc. Based on the gate driver, this paper has proposed a current measuring circuit for IGBT collector current. The circuit is used to conduct non-intervention on-line measurement of IGBT collector current by detecting the voltage drop of the IGBT power emitter and the auxiliary emitter terminals. A theoretical analysis verifies the feasibility of this circuit. The circuit adopts an operational amplifier for impedance isolation to prevent the measuring circuit from affecting the dynamic performance of the IGBT. Due to using the scheme for integration first and amplification afterwards, the difficult problem of achieving high accuracy in the transient-state and on-state measurement of the voltage between the terminals of IGBT power emitter and the auxiliary emitter (uEe) has been solved. This is impossible for a conventional detector. On this basis, the adoption of a two-stage operational amplifier can better meet the requirements of high bandwidth measurement under the conditions of a small signal with a large gain. Finally, various experiments have been carried out under the conditions of several typical loads (resistance-inductance load, resistance load and inductance load), different IGBT junction temperatures, soft short-circuits and hard short-circuits for the on-line measurement of IGBT collector current. This is aided by the capacitor voltage which is the integration result of the voltage uEe. The results show that the proposed method of measuring IGBT collector current is feasible and effective.

A Study on the Reverse-Power-Flow Phenomenon due to Transformer Wiring Types in Distribution System (배전계통에서 변압기 결선에 의한 역 조류현상에 관한 연구)

  • Shin, Dong-Yeol;Ha, Bok-Nam;Jung, Won-Wook;Cha, Han-Ju
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.22 no.9
    • /
    • pp.111-119
    • /
    • 2008
  • As the penetration of distributed generation systems is recently high, there have been metering errors, trips of protective devices in KEPCO distribution systems including an occurrence of false fault-indicator in distribution automation system. The cause of malfunctions was the reverse-power-flow phenomenon due to transformer wiring types. By the effect of the reverse-power-flow, each of phase's fundamental currents was added by about 3 times on the neutral line. A new method based on the analysis of the reverse-power-flow is proposed in this paper. Fault currents on each section were analyzed by the proposed method, and the effect of types of transformer wiring was examined experimentally. In order to reduce the malfunctions due to the reverse-power-flow, controlling the zero-sequence impedance of transformer was designed and verified by using PSCAD/EMTDC software.

A Facile Process for Surface Modification with Lithium Ion Conducting Material of Li2TiF6 for LiMn2O4 in Lithium Ion Batteries

  • Kim, Min-Kun;Kim, Jin;Yu, Seung-Ho;Mun, Junyoung;Sung, Yung-Eun
    • Journal of Electrochemical Science and Technology
    • /
    • v.10 no.2
    • /
    • pp.223-230
    • /
    • 2019
  • A facile method for surface coating with $Li_2TiF_6$ which has a high lithium-ion conductivity, on $LiMn_2O_4$ spinel cathode material for high performance lithium ion batteries. The surface coating is performed by using a co-precipitation method with $Li_2CO_3$ powder and $H_2TiF_6$ solution under room temperature and atmospheric pressure without special equipment. Total coating amount of $Li_2TiF_6$ is carefully controlled from 0 to 10 wt.% based on the active material of $LiMn_2O_4$. They are evaluated by a systematic combination of analyses comprising with XRD, SEM, TEM and ICP. It is found that the surface modification of $Li_2TiF_6$ is very beneficial to high cycle life and excellent rate capability by reducing surface failure and supporting lithium ions transportation on the surface. The best coating condition is found to have a high cycle life of $103mAh\;g^{-1}$ at the 100th cycle and a rate capability of $102.9mAh\;g^{-1}$ under 20 C. The detail electrochemical behaviors are investigated by AC impedance and galvanostatic charge and discharge test.

Cell-SELEX Based Identification of an RNA Aptamer for Escherichia coli and Its Use in Various Detection Formats

  • Dua, Pooja;Ren, Shuo;Lee, Sang Wook;Kim, Joon-Ki;Shin, Hye-su;Jeong, OK-Chan;Kim, Soyoun;Lee, Dong-Ki
    • Molecules and Cells
    • /
    • v.39 no.11
    • /
    • pp.807-813
    • /
    • 2016
  • Escherichia coli are important indicator organisms, used routinely for the monitoring of water and food safety. For quick, sensitive and real-time detection of E. coli we developed a 2'F modified RNA aptamer Ec3, by Cell-SELEX. The 31 nucleotide truncated Ec3 demonstrated improved binding and low nano-molar affinity to E. coli. The aptamer developed by us out-performs the commercial antibody and aptamer used for E. coli detection. Ec3(31) aptamer based E. coli detection was done using three different detection formats and the assay sensitivities were determined. Conventional Ec3(31)-biotin-streptavidin magnetic separation could detect E. coli with a limit of detection of $1.3{\times}10^6CFU/ml$. Although, optical analytic technique, biolayer interferometry, did not improve the sensitivity of detection for whole cells, a very significant improvement in the detection was seen with the E. coli cell lysate ($5{\times}10^4CFU/ml$). Finally we developed Electrochemical Impedance Spectroscopy (EIS) gap capacitance biosensor that has detection limits of $2{\times}10^4CFU/mL$ of E. coli cells, without any labeling and signal amplification techniques. We believe that our developed method can step towards more complex and real sample application.

Grain Boundary Trap Levels in ZnO-based Varistor (ZnO계 바리스터의 입계포획준위)

  • Kim, Myung-Chul;Park, Soon-Ja
    • Korean Journal of Materials Research
    • /
    • v.2 no.1
    • /
    • pp.12-18
    • /
    • 1992
  • The trap levels of ZnO-based varistor are obtained by Isothermal Capacitance Transient Spectroscopy method. Here ICTS measuring system consists of YHP 4192A Impedance Analyzer and a personal computer for the data acquisition. Between $-40^{\circ}C$ and $60^{\circ}C$, the grain boundary trap levels of 0.48 and 0.94eV were detected for $ZnO-Bi_2O_3-MnO$ system. The hole omission spectra are observed in the case of the addition of CoO into the $ZnO-Bi_2O_3$ system, while the electron emission spectra are detected in the case of the addition of MnO. The nonlinear resistance coefficient $\alpha$ increases with the decrease of the dormer concentration. Finally, the trap level density of $ZnO-Bi_2O_3-MnO$ system is found to decrease with the amount of CoO, while $\alpha$ is found to increase with the amount of CoO.

  • PDF

The High Power Active Filter System for Harmonic Compensation of 25kv Electric Railway (25kV 전기철도 고조파 보상을 위한 고전력 능동전력필터 시스템에 관한 연구)

  • Kim, Jae-Chul;Rho, Sung-Chan;Lee, Yoo-Kyung
    • Journal of the Korean Society for Railway
    • /
    • v.9 no.6 s.37
    • /
    • pp.761-765
    • /
    • 2006
  • At present, harmonic currents cause serious problems in power conversion system using the semiconductor switching device. Also some of the conversion system provokes harmonic currents against to the main power supply system and causes hindrances for the system. Main power impedance of the traditional LC passive filter method, influences on the filter characteristics and amplifies the harmonics when resonance phenomenon is occurred. And the traditional existing 2 level inverter systems show the limit in capacity of voltage and current in case of occurring sudden load change. So, to solve this problem active filter which uses cascaded H-bridge multi level inverter has been designed and ex-filter system circuits were totally investigated. With multi level active filtering system not only the size of filter but also the size of filter for transformer can be reduced by half and so as to the weight, while the capacity of inverter can be double sized and wave forms can be compensated exactly and precisely. Also by the benefit of the increase in rating capacity, the various currents owing to the load fluctuation can be dealt more steadily. In order to simulate the wave form of harmonics based on the measured data on the AC 25kV high speed Domestic Commercial railway, it was simulated with PSCAD/EMTDC and PSIM. Based on the results of this demonstration, the power supply system and inverter system would be more stable and also promoting its efficiency.