The Experts below are selected from a list of 29811 Experts worldwide ranked by ideXlab platform
Liu Yuan - One of the best experts on this subject based on the ideXlab platform.
-
Principle and Application of Measuring Power Transformer Wire-Wound Dc Resistance Based on Gyrator
Journal of University of South China, 2007Co-Authors: Liu YuanAbstract:The circuit model of transformer wire-wound is large inductance in series with small Resistance.The circuit for testing its Resistance is a first-order circuit,whose time constant is very large.A lot of effective methods were given for the sake of decreasing the time constant.This paper discusses the method of a model of large inductance in series with small Resistance transformed into a model of small capacitance in parallel with large Resistance by gyrator.It worked in bridge testing circuit,and the time constant decreased greatly.This is a new method for fast measuring of transformer wire-wound Dc Resistance. Hence a concrete and practical circuit was offered in this paper.
-
Rapid Measurement of Transformer Wire-wound's Dc Resistance
Journal of University of South China, 2004Co-Authors: Liu YuanAbstract:Measurement of transformer wire-wound's Dc Resistance is an important test item of transformer.A lot of effective methods were proposed to exactly and rapidly measure transformer wire-wound's Dc Resistance.However,people were not finally able to rid themselves of restriction of time constant.The paper discusses the method,where limited sample points were collected from a short portion before the start segment of dynamic current curve,and the dynamic current expression was gained by computer software fitting,thereby transformer wire-wound's Dc Resistance was measured exactly and rapidly.
Pang Yanjun - One of the best experts on this subject based on the ideXlab platform.
-
The Method of Shortening Transformer Dc Resistance Test Time
Proceedings of the 2015 International Conference on Intelligent Systems Research and Mechatronics Engineering, 2015Co-Authors: Zhao Chuanzong, Bo Liu, Liu Chuanbo, He Lishuai, Wang Chuang, Shuo Cheng, Huang Yanhai, Pang YanjunAbstract:Transformer Dc Resistance test is one of the routine test in the transformer core project, but the test efficiency is generally low.The paper ,through the analysis of transient process of large Dc Resistance measurement of transformer coil, core hysteresis phenomenon and the influence of residual magnetism on the measurement process.Improve the working principle, a method of fast measurement, large transformer Dc Resistance does not increase ,in other devices,characteristics of combination of YNd11 connection of three-phase transformer testing instrument and physical characteristics of the proposes. Field test proves that this method effectively utilizes the remanence, can get the main transformer winding Dc Resistance test results quickly and accurately. Introduction Transformer is the core equipment of electric power system in the substation, in order to ensure the safe and reliable operation, related test in the transformer factory, after installation,in operation, before and after overhaul should.At the same time, the measured data of vertical and horizontal analysis, in order to make the correct judgment on the health status of equipment. Winding Dc Resistance test can check out the contact wire and the casing state, he location of each contact state of the tap switch.Whether the actual position match to the position of the tap switch.the quality of welding joint of the winding wire, welding quality wire and winding, winding used wire specification compliance with design requirements, multi strand and around whether strand broken, whether there is inter turn short cake, lead wire fault and other fault conditions[1-3]. Winding Dc Resistance test and compared with other tests is more time-consuming, such as the 220kV main transformer routine tests of Dc Resistance test time ,accounted for the total test time of 1/3. With the progress of science and technology, the improvement of the instrument, measuring the operation more simple, measured by time shortening. But some problems also appeared in the use of the process. For example, the limited conditions , relay can not pull in the power supply low voltage , liquid crystal LCD of very low temperatures is not displayed or garbled, occasionally,the buzzer ringing of instrument discharge time is no stopping etc. It is the cause of the instrument itself, or external conditions. There are also some situation is reason of user aspects, such as sometimes in the trial process, long charging time, digital disorder etc.. In order to solve this problem, this paper analyzes some problems in practical use[4, 5]. Analysis of transient process of transformer Dc Resistance test Transformer winding in the pass into the Dc current, its equivalent circuit is shown in Figure 1.It is a first order circuit. A power supply voltage of US, inductance L, winding Resistance is R, because the initial conditions for the io-=0, the circuit response to a first-order zero state response. Differential equation of electric circuit: US=Ldi/dt+iR Solution i=US/R∙(1-e), τ=L/R Charge current speed which achieve the steady state I = US / R depends on the time constant τ. The general circuit is switched on after 5 τ ,current has reached steady state value of 99.3%
Lev Gasparov - One of the best experts on this subject based on the ideXlab platform.
-
Measurement of the Dc Resistance of semiconductor thin film–gas systems: Comparison to several transport models
Journal of Applied Physics, 2007Co-Authors: Barbara Carrico, J. Saredy, J. L. Tracy, N. G. Patel, J. Garner, Lev GasparovAbstract:Measurements have been made of the Dc Resistance of a thin film semiconductor, an indium tin oxide that has been exposed to various gases (acetylene, methane, and sulfur dioxide). The Resistance versus time is found to be a characteristic that serves as a possible means for detecting and identifying a gas. Three simple Dc transport models are used to determine the time-dependent Resistance: resistor network, dynamic Maxwell-Garnett Theory (DMGT), and a dynamic effective medium approximation (DEMA) model. The resistor network model gives only the general trend of the experimental data. The DEMA and DMGT predictions are nearly identical and independent of dimensionality. This promising application of the historic EMA and MGT models yields results that are in good agreement with experimental Resistance data presented in this paper. Future directions might include an extension of these Dc Resistance results to the finite frequency ac and optical conductivity.
S.l. Mraz - One of the best experts on this subject based on the ideXlab platform.
-
use of ac impedance conductance and Dc Resistance for determining the reliability of vrla battery systems
International Telecommunications Energy Conference, 1993Co-Authors: M S Sudhan, T.m. Noveske, L.s. Holden, S.l. MrazAbstract:The reliability of valve-regulated lead-acid (VRLA) cells has been an issue in the light of the relative immaturity of this technology. AC impedance/conductance is being promoted as a means of determining their 'state of health', as signified by their ability to perform electrically to end of life. Claims have been made that the higher the conductance, or the lower the impedance, the better the battery. The authors' efforts have focussed on evaluating this and similar techniques towards the goal of determining VRLA battery performance and reliability. Impedance and conductance measurements were made on large number of VRLA cells and batteries in the size range of 25 to over 2000 Ah, using several different commercially available meters. Data on new as well as naturally and artificially aged cells and batteries are discussed as are extended performance data and teardown analysis of cells at end of life. Results from Dc Resistance, measured by a voltage-relaxation technique, are also compared and correlated with that from impedance/conductance. >
-
Use of AC impedance/conductance and Dc Resistance for determining the reliability of VRLA battery systems
Proceedings of Intelec 93: 15th International Telecommunications Energy Conference, 1993Co-Authors: T.m. Noveske, L.s. Holden, S.l. MrazAbstract:The reliability of valve-regulated lead-acid (VRLA) cells has been an issue in the light of the relative immaturity of this technology. AC impedance/conductance is being promoted as a means of determining their 'state of health', as signified by their ability to perform electrically to end of life. Claims have been made that the higher the conductance, or the lower the impedance, the better the battery. The authors' efforts have focussed on evaluating this and similar techniques towards the goal of determining VRLA battery performance and reliability. Impedance and conductance measurements were made on large number of VRLA cells and batteries in the size range of 25 to over 2000 Ah, using several different commercially available meters. Data on new as well as naturally and artificially aged cells and batteries are discussed as are extended performance data and teardown analysis of cells at end of life. Results from Dc Resistance, measured by a voltage-relaxation technique, are also compared and correlated with that from impedance/conductance.
Liu Zhen-ling - One of the best experts on this subject based on the ideXlab platform.
-
Power Transformer Winding Dc Resistance Testing and Analysis
Central China Electric Power, 2009Co-Authors: Liu Zhen-lingAbstract:Introduced the analysis and processing of a transformer with three-phase winding of Dc Resistance imbalanced defect,through further analysis of the after processed Dc Resistance,believed the transformer still existing the polarity selector"—" side contact deficiency,further on finding out the method of comparing corresponding Dc Resistance difference rate at each tap has the advantage to detect the polarity selector defect more accurately more sensitively and more directly.Also,several points were noticed on the testing of transformer winding Dc Resistance.