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.

Calibration for time domain propagation constant measurements on power cables

Abstract: A method has been developed for characterizing the wave propagation properties of medium voltage (MV) power cables. It delivers the complex propagation constant of lossy cable transmission lines as a function of frequency. The technique is based on time domain measurements and frequency domain analysis of short pulse propagation. Particular attention is paid to the calibration, as samples with arbitrary characteristic impedances can cause multiple reflections in the test setup. The influence of numerical artefacts is also investigated. The developed technique is demonstrated on MV crosslinked polyethylene (XLPE) cables. The results are verified by comparison with frequency domain measurements of the cable S-parameters.

Extraction and modeling of self-heating and mutual thermal coupling impedance of bipolar transistors

Abstract: A measurement system comprised of an ultra-low-distortion function generator, lock-in amplifier, and semiconductor parameter analyzer is used for sensitive extraction of the small-signal thermal impedance network of bipolar devices and circuits. The extraction procedure is demonstrated through measurements on several silicon-on-glass NPN test structures. Behavioral modeling of the mutual thermal coupling obtained by fitting a multipole rational complex function to measured data is presented.

The Reflected Impedance of a Circular Coil in the Proximity of a Semi-Infinite Medium

Abstract: Most analyses on a circular coil when used in the eddy current method for nondestructive testing are empirical. Theories based on simple models are often inadequate to account for some experimental observations when the spacing between the coil and the material became small. In the present paper this problem is formulated as a boundary value problem. Wave equations of the magnetic vector potential are solved. The change in the coil impedance, when placed above a semi-infinite medium, is obtained by means of the induced voltage method, which is shown to depend only on the ? component of the magnetic vector potential. This change in impedance is found to be dependent on a number of factors: the shape and size of the coil; the spacing between the coil and the metal; the thickness, conductivity, and composition of the material, etc. Numerical computations are discussed for a few selected materials in connection with experimental results obtained elsewhere. The comparison made lent support to the present analysis. Extension of this method to the case of a stratified media is included.

Battery Impedance Analysis Considering DC Component in Sinusoidal Ripple-Current Charging

Abstract: Sinusoidal ripple-current (SRC) charging is a new charging technique that the sinusoidal current superposed with the direct current (dc) charges the battery at the frequency where the battery-alternating current (ac)-impedance reaches a minimum. However, in analyzing the effect on the SRC charging, the dc component of the SRC has not been considered until now. This paper presents a battery impedance analysis when the dc component is considered in the SRC charging. The real battery impedance is analyzed by using an electrical second-order RC battery model and overpotential voltage waveforms. The result shows that the real battery impedance is not minimized at the minimum-ac-impedance frequency. Due to this, in comparison with the constant current (CC)-constant voltage (CV) charging, the charging time, charging amount, and charging efficiency of the SRC-CV charging are not significantly different from those of the CC-CV charging. Rather, due to the ac component, the SRC-CV charging deteriorates the RMS current and maximum rising temperature by 22.5% and 18%, respectively. Also, this paper presents that the CC-CV charging using a slightly larger dc is more suitable for practical applications, since its current stress, charging time, and maximum rising temperature are improved by 2%, 9.7%, and 8.5%, respectively, in comparison with the SRC-CV charging.

Impedance parameters and the state-of charge. I. Nickel-cadmium battery

Abstract: The problem of nondestructive determination of the state-of-charge of nickel-cadmium batteries has been examined experimentally as well as theoretically from the viewpoint of internal impedance. It is shown that the modulus of the impedance is mainly controlled by diffusion at all states of charge. Even so, a prediction of the state of charge is possible if the equivalent series/parallel capacitance or the alternating current phase shift is measured at a sufficiently low a.c. test frequency (5–30 Hz) which also avoids inductive effects. These results are explained on the basis of a uniform transmission-line analog equivalent circuit for the battery electrodes.