scispace - formally typeset
Search or ask a question
Topic

Electrical impedance

About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.


Papers
More filters
Journal ArticleDOI
TL;DR: A numerically solved least squares fitting process is proposed to estimate the impedance parameters of a fractional order model of supercapacitors from their voltage excited step response, without requiring direct measurement of the impedance or frequency response.
Abstract: In this paper, we propose using a numerically solved least squares fitting process to estimate the impedance parameters of a fractional order model of supercapacitors from their voltage excited step response, without requiring direct measurement of the impedance or frequency response. Experimentally estimated parameters from low capacity supercapacitors of 0.33, 1, and 1.5 F in the time range 0.2-30 s and high capacity supercapacitors of 1500 and 3000 F in the time range 0.2-90 s verify the proposed time domain method showing less than 3% relative error between the simulated response (using the extracted fractional parameters) and the experimental step response in these time ranges. An application of employing supercapacitors in a multivibrator circuit is presented to highlight their fractional time-domain behavior.

170 citations

Journal ArticleDOI
TL;DR: An active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach and can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas.
Abstract: Impedance metasurface is composed of electrical small scatters in two dimensional plane, of which the surface impedance can be designed to produce desired reflection phase. Tunable reflection phase can be achieved by incorporating active element into the scatters, but the tuning range of the reflection phase is limited. In this paper, an active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach. The unit cell of the metasurface is a multiple resonance structure with two resonance poles and one resonance zero, capable of providing 360° reflection phase variation and active tuning within a finite frequency band. Linear reflection phase tuning can also be obtained. Theoretical analysis and simulation are presented and validated by experiment at microwave frequency. The proposed approach can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas.

170 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a different approach to analyze the high and medium frequency arcs and the low frequency diffusional tail using convenient (simplified) equivalent circuits derived from a quite general description of impedance due to a particulate (porous) system.
Abstract: In the literature, the interpretation of electrochemical impedance spectra measured on insertion cathode materials is far from being unique. In most cases, various arbitrarily selected equivalent circuits have been used for analysis of spectra whereby the criterion of merit has mainly been the quality of fit. Herein, we propose a different approach. We try to explain the main features such as the high and medium frequency arcs and the low frequency diffusional tail using convenient (simplified) equivalent circuits derived from a quite general description of impedance due to a particulate (porous) system. The proposed models have a clear physical background. The meaning of selected circuit parameters is experimentally verified using carefully modeled experiments on LiFeP0 4 and LiCoO 2 materials. In particular, we discuss the effects of state of charge, external pressure, electrode mass (thickness), and electrolyte concentration on the measured and simulated equivalent circuits. In the last part, we discuss in certain depth the complications arising from poor electronic or ionic contacting (wiring) between different phases constituting electrodes.

170 citations

Proceedings ArticleDOI
27 Sep 2004
TL;DR: In this paper, an impedance model of the proton exchange membrane fuel cell stack (PEMFCS) is proposed to evaluate the effects of ripple currents generated by the power-conditioning unit.
Abstract: In this paper an impedance model of the proton exchange membrane fuel cell stack (PEMFCS) is proposed The proposed study employs an equivalent circuit of the PEMFCS derived by frequency response analysis (FRA) technique An equivalent circuit for the fuel cell stack is developed to evaluate the effects of ripple currents generated by the power-conditioning unit The calculated results are then verified by means of experiments on three commercially available fuel cells: Avista Labs SR-12 (500 W), Ballard Nexa (12 kW) and BCS-Tech (300 W) PEMFC system The relationship between ripple current and fuel cell performance: such as power loss and fuel consumption is investigated Experimental results show that the ripple current can contribute up to 10% reduction in the available output power

170 citations

Proceedings ArticleDOI
08 May 1995
TL;DR: In this paper, a high-frequency-electrical-impedance-signature-based technique for structural integrity monitoring is presented, which relies on tracking the highfrequency (typically > 50 kHz) point impedance of the structure to identify damage.
Abstract: A high-frequency-electrical-impedance-signature-based technique for structural integrity monitoring is presented. The technique which has been under investigation at the Center for Intelligent Material Systems and Structures at Virginia Tech for the last 18 months is unique and different from conventional non-destructive damage identification and structural integrity monitoring methods. It relies on tracking the high-frequency (typically > 50 kHz) point impedance of the structure to identify damage. At such high frequencies, the technique is comparable in sensitivity to sophisticated traditional NDE techniques, such as ultrasonics, and is capable of qualitatively detecting incipient-type damage by looking at changes in structural impedance. As yet, it can be implemented in a remote sensing scenario with small non- intrusive piezoelectric (PZT) materials. The structure's high-frequency electrical impedance signature, which is functionally equivalent to its mechanical impedance signature, is obtained through a bonded PZT functioning both as actuator and sensor. A statistic algorithm based on the difference in the electrical impedance of a healthy and a damaged structure, is then applied to extract an index of the health of the structure. High-frequency excitation, which is greatly facilitated by the electrically driven low-power compact PZT patch, assures a clearly visible change in the impedance/vibration signature even for very minor damage/changes. It also limits the actuation/sensing area to a small region, `local-area', close to the PZT patch. Because of the limited actuation/sensing area, the impedance signature is affected only by changes in the structural properties close to the sensor-actuator and is insensitive to changes in far-field boundary conditions, mass loading, etc., which may be part of the normal usage of the structure. As a case study, an application to a real complex aircraft structure is presented. Experimental proof that very minor alterations in the structure are easily identified and the fact that the detection range of the bonded PZT actuator/sensor is constrained to its immediate neighborhood is presented.

170 citations


Network Information
Related Topics (5)
Voltage
296.3K papers, 1.7M citations
87% related
Capacitor
166.6K papers, 1.4M citations
85% related
Amplifier
163.9K papers, 1.3M citations
85% related
Dielectric
169.7K papers, 2.7M citations
81% related
Electromagnetic coil
187.8K papers, 1.1M citations
80% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,514
20223,479
20211,009
20201,579
20191,924
20181,809