• Title, Summary, Keyword: steady-state current

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A simplified method to determine the chloride migration coefficient of concrete by the electric current in steady state

  • Lin, K.T.;Yang, C.C.
    • Computers and Concrete
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    • v.13 no.1
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    • pp.117-133
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    • 2014
  • This study presents a rapid method for determining the steady state migration coefficient of concrete by measuring the electric current. This study determines the steady state chloride migration coefficient using the accelerated chloride migration test (ACMT). There are two stages to obtain the chloride migration coefficient. The first stage, the steady-state condition was obtained from the initial electric current at the beginning of ACMT. The second stage, the average electrical current in the steady state condition was used to determine the steady state chloride migration coefficient. The chloride migration coefficient can be determined from the average steady state current to avoid sampling and analyzing chlorides during the ACMT.

Steady-State Current Characteristics for Squirrel Cage Induction Motor according to Design Variables of Rotor Bars using Time Difference Finite Element Analysis

  • Kim, Young Sun
    • Journal of Magnetics
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    • v.22 no.1
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    • pp.104-108
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    • 2017
  • Induction motors have wide applicability in many fields, both in industrial sectors and households, for their advantages of a high efficiency and robust structure. The introduction of power-source-containing harmonics into the induction motor winding lowers its efficiency and increases its temperature, greatly affecting its operation characteristics. In this study, we performed an electromagnetic field analysis using the time-difference finite-element method with the purpose of analyzing the steady-state current characteristics of an induction motor. Additionally, we calculated the steady-state current with a method combining an electromagnetic field equation and a circuit equation. In the electromagnetic field analysis, the nonlinearity was taken into account using the Newton-Raphson method, and a backward time-difference method was employed for the time derivative term. Then, we compared the steady-state current of the induction motor obtained by calculation with the experimentally measured values, thus validating the proposed algorithm. Furthermore, we analyzed the impacts of the shape and material of the rotor conductor bar of the induction motor on the steady-state current of the main winding.

Modeling and Steady-state Analysis of the Multi-Phase Interleaved Buck converter in Discontinuous Inductor Current Mode (불연속 전류모드에서의 다상 교호 강압컨버터의 정상상태 해석 및 모델링)

  • Chang, Sung-Dong;Jang, Eun-Sung;Chung, Se-Kyo;Shin, Hwi-Boem;Lee, Hyun-Woo
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.506-510
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    • 2004
  • A multi-phase interleaved buck converter is used to reduce current ripples and filter size of a power supply. This paper addresses the modelling and steady-state analysis of the multi-phase interleaved buck converter operated in discontinuous inductor current mode. The model is derived using an averaging technique in steady state. The do voltage ratio and the range of the discontinuous inductor current mode(DICM) and the continuous output current mode(COCM) are derived from the averaged state-space model. In addition, the efficiency is investigated according to the number of phase.

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An Improved Stationary Frame-based Digital Current Control Scheme for a PM Synchronous Motor

  • Kim, Kyeong-Hwa;Young, Myung-Joong
    • Journal of Power Electronics
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    • v.1 no.2
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    • pp.88-98
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    • 2001
  • An improved stationary frame-based digital current control technique for a permanent magnet(PM) synchronous motor is presented. Generally, the stationary frame current controller is known to provide the advantage of a simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state. On the other hand, in the synchronous frame current regulator the regulated currents are dc quantities and a zero steady-state error can be obtained through the integral control. However, the need to transform the signals between the stationary and synchronous frames makes the implementation of a synchronous frame regulator complex. Although the PI controller in the stationary frame gives a steady-state error and a phase delay, the control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF., resulting in an ideal steady-state control characteristics irrespective of an operating condition as in the synchronous PI decoupling controller. However, its steady-state response may be degraded due to the inexact cancellation inputs under the parameter variations. To improve the control performance in the stationary frame, the disturbance is estimated using the time delay control. The proposed scheme is implemented on a PM synchronous motor using DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.

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An Improved Stationary Frame-based Digital Current Control Scheme for a PM Synchronous Motor

  • Kim Kyeong-Hwa;Youn Myung-Joong
    • Proceedings of the KIPE Conference
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    • pp.174-178
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    • 2001
  • An improved stationary frame-based digital current control technique for a permanent magnet (PM) synchronous motor is presented. Generally, the stationary frame current controller is known to provide the advantage of a simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state. On the other hand, in the synchronous frame current regulator, the regulated currents are dc quantities and a zero steady-state error can be obtained through the integral control. However, the need to transform the signals between the stationary and synchronous frames makes the implementation of a synchronous frame regulator complex. Although the PI controller in the stationary frame gives a steady-state error and a phase delay, the control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF, resulting in an ideal steady-state control characteristics irrespective of an operating condition as in the synchronous PI decoupling controller. However, its steady-state response may be degraded due to the inexact cancellation inputs under the parameter variations. To improve the control performance in the stationary frame, the disturbance is estimated using the time delay control. The proposed scheme is implemented on a PM synchronous motor using DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.

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Design of Superconducting Current Leads Considering Bifurcation Characteristic (분지 특성을 고려한 초전도 전류도입선 설계)

  • 설승윤
    • Progress in Superconductivity and Cryogenics
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    • v.1 no.2
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    • pp.37-42
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    • 1999
  • The stability of high-temperature superconducting current leads for cryogenic devices are investigated. By assuming full transition from superconducting state to normal state at a transition temperature, the HTS current at a transition temperature, the HTS current lead shows bifurcation phenomenon. There is a bifurcation shape-factor, HTS leads have three steady state. Below the bifurcation shape-factor, the superconducting current lead is unconditionally stable, because there exists only one steady-factor HTS current lead is conditionally stable depending on the shape and intensity of disturbance.

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Quasi-Steady-State Analysis on the Effect of the STATCOM on FRT Performance of Fixed Speed Wind Turbines (준정상상태 해석을 통한 고정속 풍력 발전기의 FRT에 대한 STATCOM의 효과 분석)

  • Ahn, Seon-Ju;Hwang, Pyeong-Ik;Nam, Soon-Ryul;Kang, Sang-Hee;Moon, Seung-Il
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.4
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    • pp.686-692
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    • 2010
  • This paper analyzes the effect of the STATCOM on the improvement of the Fault Ride Through (FRT) capability of the fixed speed wind turbines(FSWTs). The steady-state models of the wind farm components, such as induction generator, capacitor bank, and the STATCOM, are developed based on the simplified equivalent circuit. Especially, the STATCOM is modeled as a controllable current source and a method that analytically determines the magnitude of the injection current is developed. For the quasi-steady-state(QSS) analysis, the steady-state model of the generator and STATCOM are merged with the dynamic model of drive train. The QSS simulation with the STATCOM shows that the STATCOM can enhance the FRT performance by improving the $W_r-T_e$ characteristics of the FSWTs.

Stability Analysis ofn HTS Current Lead with Constant Safety Factor (안전율이 일정한 초전도 전류도입선의 안정성해석)

  • Seol, Seoung-Yun
    • Progress in Superconductivity and Cryogenics
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    • v.2 no.2
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    • pp.15-19
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    • 2000
  • The stability of variable cross-sectional area HTS current lead is considered. The cross-sectional area is varied to have a constant safety factor which is defined as the ratio of operating current and critical current of superconductor. As the constant area HTS lead, the variable cross-sectional area HTS lead also has three steady states above the bifurcation point and only one steady state below the bifurcation point. The temperature profiles and current sharing ratios for each steady state are calculated. The heat dissipation into cryogenic system for super-conducting, intermediate, and upper states are compared. For Bi-2333 sheathed with silver-gold alloy 2m length of current lead, and the maximum temperature of upper state seems to be burn-out free below 5m length.

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Steady-State Analysis of N-phase Interleaved Boost Converter (N상 Interleaved Boost 컨버터의 정상상태 특성 해석)

  • 박종규;장성동;신휘범;김흥근
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.53 no.3
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    • pp.196-205
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    • 2004
  • Although many papers about the interleaved boost converter(IBC) have been published, there are, unfortunately, no analytical and rigorous expressions for steady-state operation of the N-phase IBC. To understand the operating characteristics of the N-phase IBC, the averaged state equation and the general steady-state solutions are derived in this paper. The general expressions of the current unbalance due to the parameter mismatch, the inductor and input current ripples, and the output voltage ripple are also presented. Through the analytical expressions presented, the steady-state characteristics of the N-phase IBC are analyzed theoretically and verified experimentally.

Steady-State Characteristic Analysis of Single-Phase Line-Start Permanent Magnet Synchronous Motor (단상 영구자석형 유도동기기의 정상상태 특성해석)

  • Kang, Gyu-Hong;Nam, Hyuk;Hong, Jung-Pyo
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.2
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    • pp.53-60
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    • 2003
  • This paper deals with steady-state analysis of a single-phase line-start permanent magnet synchronous motor. In order to analyze the steady-state characteristics, the asymmetric single-phase line-start synchronous motor is converted to the symmetric two-phase synchronous motor, that is, the asymmetric magnetic field is separated from the positive and the negative symmetric components using symmetrical-component theory. The analysis method of the synchronous motor on the d-q axis coordinates is used for the positive component and the equivalent circuit of the induction motor is applied for the negative component analysis. Moreover, d-q axis inductance considering current phase angle is applied to positive component analysis for precise characteristic analysis. In order to validate the proposed analysis method, the analysis results are compared with the experimental results.