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.

Impedance Spectroscopy: Applications to Electrochemical and Dielectric Phenomena

Abstract: Preface ix 1. Fundamentals of electrochemical impedance spectroscopy 1 2. Graphical representation of impedance spectroscopy data 23 3. Equivalent-circuit elements and modeling of the impedance phenomenon 37 4. Examples of ideal equivalent circuit models 49 5. Impedance representation of bulk-material and electrode processes 59 6. Distributed impedance models 97 7. Impedance analysis of complex systems 113 8. Impedance Instrumentation, testing, and data validation 163 9. Selected examples of impedance-analysis applications: electroactive polymer films 205 10. Selected examples of EIS analysis applications: industrial colloids and lubricants 219 11. Selected examples of EIS analysis applications: cell suspensions, protein adsorption, and implantable biomedical devices 247 12. Selected examples of impedance-analysis applications 281 13. Impedance-spectroscopy modifications 319 14. Conclusions and perspectives of EIS 333 Abbreviations and Symbols 335 Index 345

Analysis, Design, and Implementation of Virtual Impedance for Power Electronics Interfaced Distributed Generation

Abstract: This paper presents a virtual impedance design and implementation approach for power electronics interfaced distributed generation (DG) units. To improve system stability and prevent power couplings, the virtual impedances can be placed between interfacing converter outputs and the main grid. However, optimal design of the impedance value, robust implementation of the virtual impedance, and proper utilization of the virtual impedance for DG performance enhancement are key for the virtual impedance concept. In this paper, flexible small-signal models of microgrids in different operation modes are developed first. Based on the developed microgrid models, the desired DG impedance range is determined considering the stability, transient response, and power flow performance of DG units. A robust virtual impedance implementation method is also presented, which can alleviate voltage distortion problems caused by harmonic loads compared to the effects of physical impedances. Furthermore, an adaptive impedance concept is proposed to further improve power control performances during the transient and grid faults. Simulation and experimental results are provided to validate the impedance design approach, the virtual impedance implementation method, and the proposed adaptive transient impedance control strategies.

Electric impedance of the squid giant axon during activity.

Abstract: Alternating current impedance measurements have been made over a wide frequency range on the giant axon from the stellar nerve of the squid, Loligo pealii, during the passage of a nerve impulse. The transverse impedance was measured between narrow electrodes on either side of the axon with a Wheatstone bridge having an amplifier and cathode ray oscillograph for detector. When the bridge was balanced, the resting axon gave a narrow line on the oscillograph screen as a sweep circuit moved the spot across. As an impulse passed between impedance electrodes after the axon had been stimulated at one end, the oscillograph line first broadened into a band, indicating a bridge unbalance, and then narrowed down to balance during recovery. From measurements made during the passage of the impulse and appropriate analysis, it was found that the membrane phase angle was unchanged, the membrane capacity decreased about 2 per cent, while the membrane conductance fell from a resting value of 1000 ohm cm.2 to an average of 25 ohm cm.2 The onset of the resistance change occurs somewhat after the start of the monophasic action potential, but coincides quite closely with the point of inflection on the rising phase, where the membrane current reverses in direction, corresponding to a decrease in the membrane electromotive force. This E.M.F. and the conductance are closely associated properties of the membrane, and their sudden changes constitute, or are due to, the activity which is responsible for the all-or-none law and the initiation and propagation of the nerve impulse. These results correspond to those previously found for Nitella and lead us to expect similar phenomena in other nerve fibers.

A simple three-terminal IC bandgap reference

Abstract: A new configuration for realization of a stabilized bandgap voltage is described. The new two-transistor circuit uses collector current sensing to eliminate errors due to base current. Because the stabilized voltage appears at a high impedance point, the application to circuits with higher output voltage is simplified. Incorporation of the new two-transistor cell in a three-terminal 2.5-V monolithic reference is described. The complete circuit is outlined in functional detail together with analytical methods used in the design. The analytical results include sensitivity coefficients, gain and frequency response parameters, and biasing for optimum temperature performance. The performance of the monolithic circuit, which includes temperature coefficients of 5 ppm//spl deg/C over the military temperature range, is reported.