Capacitive Reactance Research Articles

The Signal Injection Method with High-Frequency for Distribution Network Capacitive Current Measurement

In order to solve the problem of limited frequency selection range and simplify calculations on the grounded capacitance measurement for the ungrounded distribution system, a high-frequency injecting method for the capacitive current measurement is proposed in the paper. The injecting frequency can be high enough to ignore capacitive reactance and leakage resistance comparing with leakage inductance. The leakage inductance value is obtained directly on the base of simplified calculation. Then the resonant frequency of the power system needs to be obtained by the traditional resonant method. Finally, the grounded capacitance can be calculated through the equivalent circuit and the simultaneous equations. The simulation and experiments verify the feasibility of the high-frequency method. The experiment results prove that this method not only solves the problem of frequency selection, but also has advantages of convenience and high precision (the relative error is less than 5%), which is also suitable for the larger grounded capacitance system.

Formation of Fe-19 wt%Cr-9 wt%Ni Nanocrystalline Alloy with Excellent Corrosion Resistance: Phase Transition and Microstructure

In this paper, microstructure characteristics and phase transitions of Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy are comprehensively studied during the mechanical alloying and hot pressing sintering processes. Corrosion resistance of the sintered Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy samples is further analyzed. During the mechanical alloying process, Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy powders mainly composed of metastable ferrite phase are obtained after mechanical alloying for 8, 16 and 24 h, respectively. In the subsequent hot pressing sintering process, the phase transitions (from ferrite to austenite) occur from 650 to 750 °C for Fe-19 wt%Cr-9 wt%Ni alloy powders milled for 24 h. When the sintering temperature is raised to 1050 °C for 1 h, the ferrite phase has transformed into austenite phase completely, and the obtained grain size of sintered Fe-19 wt%Cr-9 wt%Ni alloy is around 40 nm. Electrochemistry test of the sintered Fe-19 wt%Cr-9 wt%Ni alloy has been operated in 0.5 mol L−1 H2SO4 solution to show the corrosion resistance properties. Results show that the sintered Fe-19 wt%Cr-9 wt%Ni alloy exhibits excellent corrosion resistance, which is proved by higher self-corrosion potential, lower self-corrosion current density and larger capacitive reactance, compared with that of commercial 304 stainless steel.

Numerical Simulation of Improvement of Voltage Profile and Reliability by Efficient Placement of Distributed Generation in Grid Connected System

Many studies have been performed on the positioning of ideal capacitors in appropriation systems for the purposes of power factor modification, voltage profile enhancement, and loss reduction. Mechanical plants with variable load conditions, in particular, have large inductive loads and a low power factor. Much of the time, a client's primary reason for building a capacitor bank is to keep a strategic distance from power bill penalties. The power factor is a ratio of true power to apparent power that indicates how much true power electrical equipment absorbs. Inductive or capacitive reactance, as well as harmonics in the circuit, induce a power factor of some importance other than solidarity. By minimizing power losses, the framework could be able to achieve a longer life expectancy and improved dependability. By choosing the right size, area, and cost of capacitor bank, different techniques have been used to minimize power losses financially. The issue of capacitor allocation in electrical distribution systems involves rising energy and lowering pinnacle power misfortune by capacitor establishment methods. This paper introduces a novel method for evaluating framework competitor hubs in a capacitor structure conveyance device using inexact thought. The capacitor placement technique is divided into two sections: to some extent one, misfortune affectability factors are used to choose the up-and-comer areas for the capacitor situation, and to a lesser extent two, the genetic algorithm technique is used to recognize the capacitor measures for minimizing energy losses and improving voltage profiles through capacitor placement. The proposed strategy is implemented on the IEEE-34 bus system, and the target feature is achieved using a genetic algorithm and enhanced particle swarm optimization. For the test case, the implemented device performed well in terms of loss reduction and voltage profile change.

Dry electrochemical polishing of copper alloy in a medium containing ion-exchange resin.

Metal surfaces can be polished effectively and in an environmentally friendly way by virtue of the mechanical and electrochemical interaction between ion-exchange resin particles and the metal substrate. This paper studied this ‘dry’ polishing process and its property effects on 65 brass alloys. Surface morphology analysis revealed that the surface roughness can be reduced by over 71.5% from 0.764 ± 0.031 μm to 0.218 ± 0.080 μm with longer polishing time, and by over 67.1% from 0.764 ± 0.031 μm to 0.252 ± 0.02 μm with higher voltage. XPS and EDS results showed that only a small amount of oxygen species remained on the polished metal surface, while Cu and Zn were apparently present in the metallic state. The decrease in self-corrosion current indicated by the Tafel curves and the increase in the radius of the capacitive reactance circle contained in the Nyquist plots indicate that the surface corrosion resistance of the polished materials has been improved.

Damping sub-synchronous resonance and improving fault ride through capability: Using S.T.A.T.C.O.M. and S.D.B.R. in a wind power system

Concerning wind power penetration into power systems in recent years, the problems of incorrect operation of wind turbines include sub-synchronous resonance (S.S.R.) oscillations and fault ride through (F.R.T.) capabilities need to be fully considered and resolved. In this respect, the S.S.R. phenomenon can severely damage the rotor of an asynchronous generator in a compensated power system with capacitive reactance connected to a wind turbine. Therefore, active and reactive powers of the mentioned systems are controlled by static synchronous compensator (S.T.A.T.C.O.M.) and series dynamic braking resistor (S.D.B.R.); respe­ctively. Moreover, power system designers combine them to improve system sta­b­i­lity. In this study, an appropriate method was presented based on the genetic algorithm (G.A.) to provide coordinated and optimal control of STAT­CO­M and S.D.B.R. in order to mitigate S.S.R. and enhance F.R.T. capabilities in a wind far­m connected a power system. Optimization variable of this pro­blem included resistance value of S.D.B.R., S.T.A.T.C.O.M. capability, along with its control parameters optimized simul­tane­ou­s­ly via G.A. to store kinetic energy in the rotor, to control voltage dev­ia­tions of the wind farm bus, and to minimize speed deviations of the rotor. The prop­osed method was implemented on the Institute of Electrical and Electronics Engineers (IEEE) first benchmark model to verify the performance of its control structure. The obtained results indicated that coordinated and optimal combin­ati­o­n of S.T.A.T.C.O.M. and S.D.B.R. could damp S.S.R. oscillations and augment system stability.

Investigation on barometric and hydrostatic pressure sensing properties of Pb[(Mg1/3Nb2/3)0.7Ti0.3]O3 electro-ceramics

Two-stage solid-state reaction-based intermediate columbite phase technique has been employed to fabricate the single-phase Pb[(Mg1/3Nb2/3)0.7Ti0.3]O3 (PMN-0.3 PT) electro-ceramics. The Rietveld refinement of XRD data suggests the presence of monoclinic crystal structure with space group ‘Cm’. The bulk ceramics interior looks very flat without voids and well-defined grain boundaries, which confirm the high quality single-phase microstructure. The final elemental compositions of the material are similar to the initial compositions within the instrument's experimental error. We have investigated pressure and temperature-dependent dielectric and impedance properties to test the possible applications as a pressure transducer. A well defined square hysteresis with large polarization confirms the high quality ferroelectric and piezoelectric properties. For the first time, we have studied the pressure sensing properties of PMN-0.3 PT ceramic in the range 25–250 kPa in barometric pressure using dead weights and 10–50 MPa hydraulic pressure (oil medium). The ceramic demonstrates a gradual change in capacitance as well as in capacitive reactance, with % sensitivity of 0.10 MPa−1 in the Hydraulic pressure range (10–50 MPa), and with % sensitivity of 0.02 kPa−1 in the Barometric pressure range (25–250 kPa). These results demonstrate the suitability of PMN-0.3 PT ceramic as a pressure transducer.

Effect of bismuth substitution on piezoelectric coefficients and temperature and pressure-dependent dielectric and impedance properties of lead zirconate titanate ceramics

Basic Physics as well as devices fabrication required in-depth analysis of the effect of temperature, pressure, and other physical parameters on dielectric properties to understand the microstructure-property relation. In this regard, we have thoroughly investigated the temperature and pressure dependent ferroelectric, dielectric, and impedance properties of Bi-substituted Pb1-xBi2x/3(Zr0.52Ti0.48)O3 (PBiZT) (x = 0.10 to 0.40) ceramics. The maximum solubility of Bi was found near x = 0.15, and above this composition, it shows a composite phase of PBiZT and ZrO2. The remanent polarization (Pr) increases with decrease in the Bi concentration with the maximum value obtained for x = 0.15, i.e., 40 μC/cm2. Temperature-dependent dielectric constant and tangent loss were measured as function of composition to check the ferroelectric phase transition temperature (Tc) and the operating temperature limit for the material to make a device. The Tc value increases with decrease in bismuth (Bi) concentration which obtained in the range of 350 ℃ - 375 ℃. The tangent loss was observed to be near about 0.01 to 0.03 below 200 ℃ which suggests its suitability for device applications. The temperature-dependent imaginary part of impedance (Z'') was measured at various temperatures with varying frequency in the range of 100 Hz – 1 MHz. The peaks positions of the Z'' vs. frequency shift towards lower temperature side with increasing the value of x from 0.1 to 0.4 near and above Tc. The pressure-dependent dielectric constant (εr) and capacitive reactance (Xc) were also measured for varying x, and it was observed that maximum change in εr and Xc was observed for x = 0.15 i.e. 13% and 10.5%, respectively. The pressure sensitivity was obtained maximum for the composition near the maximum solubility of Bi in PbZr1-xTixO3 (PZT) matrix. The reason behind getting the highest remanent polarization and pressure sensitivity for x = 0.15 is that of the highest piezoelectric coefficients ∼ 130 pC/N.

Study of the Protection of Aluminum Alloy Surfaces by a Graphene-Modified Fluorocarbon Anticorrosive Coating

Graphene-modified anticorrosion coatings have become a hot spot in the field of metal protection due to the large-scale promotion of aluminum alloys, which are prone to corrosion in marine and atmospheric environments. The protection of aluminum alloy surfaces by a graphene-modified anticorrosive coating was explored in this study by applying a graphene-modified anticorrosive coating to an aluminum alloy surface to test its resistance to corrosion. Dispersion-treated reduced graphene oxide (rGO) was used to modify the epoxy resin and fluorocarbon resin. It was found, by using a scanning electron microscopy (SEM) and the microstructure of the coating made by the Raman Spectroscopy Institute, that the addition of rGO could effectively improve the porosity of the epoxy primer, and the electrochemical workstation was able to resist the graphene-modified anticorrosive coating. The corrosion performance was quickly characterized, the polarization curve and the AC impedance curve were fitted, and it was found that the self-corrosion current density ( J corr ) of the graphene-modified anticorrosive coating was the smallest ( 1.190 × 10 − 7 A / c m 2 ) when 0.6% of rGO was added; the impedance modulus ( ∣ Z ∣ ) was the largest (104), the capacitive reactance arc radius was the largest, and the coating resistance was the largest after fitting (15517 Ω). When 0.8% of rGO was added, the dispersion coefficient was large, and it had a good physical insulation performance. The main reason for the reduction of the corrosion resistance was that the agglomeration of rGO made the aluminum alloy matrix and the external corrosive environment form a highly conductive circuit, thereby accelerating the corrosion of the aluminum alloy matrix.

New Contactless Conductivity Detection (CCD) Sensor for Fluid Conductivity Measurement

A new contactless conductivity detection (CCD) sensor, which is on the basis of the capacitive reactance elimination principle, is developed in this work. The CCD sensor has two AC paths, the detection path and the compensation path. The unfavorable capacitive reactance produced by the coupling capacitances in the detection path is cancelled out by the capacitive reactance produced by an introduced capacitance in the compensation path. The resolution of the CCD sensor is hence improved. Three prototypes of the new CCD sensor (the inner diameters are 0.50 mm, 1.00 mm and 1.65 mm respectively) were developed, and fluid conductivity measurement experiments were carried out to investigate the measurement performance of the CCD sensor. The experimental results show that the development of the CCD sensor is successful and the conductivity measurement accuracy is satisfactory. The research results verify that the capacitive reactance elimination principle is an effective way to overcome the unfavorable influence of the coupling capacitances on the conductivity measurement, and therefore the new CCD sensor has a very good development potential.

The Effect of Capacitance on the Power Factor Value of Parallel RLC Circuits

The power factor of the circuit is determined by the amount of pure resistance (R), self-inductance of the coil (L) and the capacitance of the capacitor (C). In this study, the measurement of the power factor value in a parallel RLC circuit was carried out through experimental testing and simulation with the value of C as the independent variable, while the values of R and L were fixed conditioned quantities. The purpose of this study was to determine the effect of capacitance on a parallel RLC circuit. One of the ways to improve the power factor value in a circuit is to install capacitive compensation using a capacitor. The relation between the power factor value and the capacitance and inductive reactance based on the experimental results and the simulation calculation results in the parallel RLC circuit both shows the same pattern with a relative uncertainty below 8%. The experimental results and simulation results both show that the power factor can be improved by using a right capacitance which is around the capacitance value when there is resonance in the circuit.

Wideband circularly polarised antenna based on interelement mutual coupling effect

This study presents a circularly polarised (CP) antenna with a wideband characteristic, which is caused by the interelement mutual coupling effect. The proposed antenna consists of a dipole array with four elements in centre symmetry and a wideband feed network. In order to extend the lowest working frequency, a strong mutual coupling effect is introduced to the adjacent co-polarisation elements. What's more, the introduced effects of capacitive coupling reactance counteract the effects of the element's inductively reactive ground plane. Then, a small, tightly coupled array is formed that possesses wide impedance bandwidth and orthogonal polarisation component. A wideband feed network, including Wilkinson power dividers, phase shifters, and impedance converters, is designed to provide amplitudes and phases excitation that circular polarisation antenna required. Finally, a prototype is fabricated and tested. Measured results show a VSWR<2 impedance bandwidth of 102.7% (2.09–6.5 GHz) and a 3-dB axial ratio bandwidth of 94.2% (2.25–6.25 GHz). Besides, a relatively stable gain is realised across the operating band.

A Plant's Electrical Parameters Indicate Its Physiological State: A Study of Intracellular Water Metabolism.

Almost all of a plant’s life activities involve electrochemical reactions. Plant electrical parameters respond quickly to environmental changes and are closely related to physiological activities. In this study, the theoretical intrinsic relationships between clamping force and leaf impedance (Z) or capacitive reactance (Xc) and capacitance (C) were revealed as 3-parameter exponential decay and linear models based on bioenergetics, respectively, for the first time. Leaf electrical characteristics including intrinsic impedance (IZ), capacitive reactance (IXc), capacitance (IC) and specific effective thickness (d) were successfully detected using the above-mentioned relationships and were used to manifest plant metabolic activity. The intracellular water-holding capacity (IWHC), water-use efficiency (IWUE), water-holding time (IWHT) and water transfer rate (WTR) of plant leaves were defined on the basis of IZ, IXc, IC and d, and applied to reflect the intracellular water metabolism. The results demonstrated that the leaves of Broussonetia papyrifera plants grown in agricultural soil had higher IC, d, IWHC, WTR, water content values and lower IZ, IXc values than those grown in moderately rocky desertified soil. The leaf IC, d, IWHC, WTR and water content values of herbaceous plants were higher than those of woody plants. Solanum tuberosum L. had higher leaf IC, d, IWHC and WTR values, but exhibited lower IZ, IXc, IWUE and IWHT values than Capsicum annuum L. This study highlighted that a plant’s electrical parameters based on bioenergetics clearly indicate its physiological process—e.g., the intracellular water metabolism.

Asymmetric Entrainment Structure of Pierce Oscillator Circuit

Experimental study is presented to uncover entrainment property of Pierce oscillator circuit (i.e., one of the most standard circuits for crystal oscillators) subject to sinusoidal external forcing. In contrast to the well-known Arnold tongues observed in a wide class of forced nonlinear systems, asymmetric shape was observed as an entrainment region of the circuit in two-dimensional parameter space spanned by the external forcing strength and frequency. Computation of the impedance curve revealed that the asymmetric shape is due to positive (inductive) or negative (capacitive) reactance of the Pierce circuit, which facilitates or inhibits the circuit oscillations. We extend this insight into two coupled Pierce circuits and show that, to efficiently achieve their synchronization, it is advantageous to drive a slow oscillator circuit by a fast circuit rather than to drive a fast circuit by a slow circuit. Our study provides a guideline on an optimal network configuration for coupled crystal oscillators, which may find applications in distributed digital clocks and wireless communication systems.

A Single-Channel Amplifier for Simultaneously Monitoring Impedance Respiration Signal and ECG Signal

Physiological signals can reflect the physiological characteristics of the human body and serve as important reference for doctors in clinical diagnosis. Hence, wearable intelligent equipment for physiological signal monitoring has attracted increasing attention. Such equipment must be of a small size and must have low power consumption. To meet these demands, we designed a single-channel amplifier, that can simultaneously acquire the electrocardiograph (ECG) signal and impedance respiration signal. We used oversampling and fast digital lock-in technology to improve the measuring precision of the circuit without increasing the complexity of the circuit. The circuit makes use of the capacitive reactance of a capacitor, which changes with the frequency of the signal; this can meet the different impedance requirements of both the impedance respiratory signal and ECG signal during the measurements. The result of experiments shows that the circuit can obtain high-quality ECG and respiratory waveforms. This circuit can serve as a valuable reference for the design of wearable health monitoring equipment to simultaneously acquire multiple human physiological signals in a signal channel.

Perfect Conversion of a TM Surface Wave Into a TM Leaky Wave by an Isotropic Periodic Metasurface Printed on a Grounded Dielectric Slab

This article presents an exact solution for a perfect conversion of a TM-polarized surface wave (SW) into a TM-polarized leaky wave (LW) using a reciprocal and lossless penetrable metasurface (MTS) characterized by a scalar sheet impedance, located on a grounded slab. On contrary to the known realizations of LW antennas, the optimal surface reactance modulation which is found here ensures the absence of evanescent higher-order modes of the field Floquet-wave expansion near the radiating surface. Thus, all the energy carried by the SW is used for launching the single inhomogeneous plane wave into space without accumulation of reactive energy in the higher-order modes. It is shown that the resulting penetrable MTS exhibits variation from an inductive to a capacitive reactance passing through a resonance. The present formulation complements a previous article of the authors, in which a perfect conversion from TM-polarized SW to TE-polarized LW was found for impenetrable boundary conditions. Here, the solution takes into account the grounded slab dispersion, and it is convenient for practical implementation.

The influence of temperature on the impedance characteristics of PEMFC

Electrochemical impedance spectroscopy (EIS) is one of the main characterization methods of PEMFC, which has important reference value for evaluating the performance of PEMFC. In this paper, the impedance curves of PEMFC at different temperatures are measured by experiments, and the equivalent circuit is used to analyze the influence of battery temperature and humidification temperature on the impedance. The study found that when the battery temperature is higher than the humidification temperature, both the ohmic impedance and the Faraday impedance increase significantly; the double layer in the PEMFC mainly embodies the capacitive reactance characteristics, and the more the humidification temperature is higher than the cell temperature, the more obvious the degree of the double layer embodies the capacitive reactance characteristics. The results of this study have a certain reference value for understanding the working principle of PEMFC and improving its performance.

Reducing MRI RF-induced heating for the external fixation using capacitive structures

This paper presents a generic method to reduce the radiofrequency (RF) induced heating of external fixation devices during the magnetic resonance imaging (MRI) procedure. A simplified equivalent circuit model was developed to illustrate the interaction between the external fixation device and the MRI RF field. Carefully designed mechanical structures, which utilize capacitive reactance from the circuit model, were applied to the external fixation device to mitigate the coupling between the external fixation device and the MRI RF field for RF-induced heating reduction. Both numerical and experimental studies were performed to demonstrate the validity of the circuit model and the effectiveness of the proposed method. By adding capacitive structures in both the clamp-pin and rod-clamp joints, the peak specific absorption rate averaged in 1 gram (SAR1g) near the pin tips were reduced from 760.4 W kg−1 to 12.0 W kg−1 at 1.5 T and 391.5 W kg−1 to 25.2 W kg−1 at 3 T from numerical simulations. Experimental results showed that RF-induced heating was reduced from 7.85 °C to 1.01 °C at 1.5 T and from 16.70 °C to 0.32 °C at 3 T for the external fixation device studied here. The carefully designed capacitive structures can be used to detune the coupling between the external fixation device and the MRI fields to reduce the RF-induced heating in the human body for both 1.5 T and 3 T MRI systems. However, as RF-induced heating is very device and design specific all devices must be thoroughly tested based on its final design.

Influence mechanism of pulse frequency on the corrosion resistance of Cu–Zn binary alloy

AbstractIn this work, the influence of pulse frequency on the corrosion resistance of Cu–Zn binary alloy has been investigated by using electrochemical workstation, scanning electron microscope and X-ray diffraction. The results have shown that after the electric pulse treatment, the average grain size in the microstructure of high-zinc binary brass decreased and the corrosion resistance increased. The thickness of dezincification layer decreased from 49.8 to 30.8 µm. The diameter of capacitive reactance arc increased from 741.1 to 2898.0 µm. The corrosion potential increased from −0.2719 to −0.2378 V, and the corrosion current density decreased from 6.3147 × 10−6 to 4.6971 × 10−7 A cm−2 by one magnitude order.

Impedancemetric-type NO2 sensor based on non-stoichiometric perovskite type sensing electrode using multiple response signals

Perovskite-type oxides have received considerable attention as sensing electrode (SE) for solid electrolyte type sensors because of their exceptional sensing performance and compositional flexibility. Herein, non-stoichiometric perovskite oxides (La0.75Sr0.25)xCrO3-δ (x = 0.95, 1.0, 1.05) with nano-structure were prepared in porous YSZ backbone by impregnation method as SE for impedancemetric-type NO2 sensor. Because of the non-stoichiometry of SE, the NO2 adsorption capacity and electrochemical activity of SE are effectively enhanced. Consequently, the sensors based on non-stoichiometric SEs exhibit noticeably improved sensitivity to NO2. Meanwhile, instead of module value (|Z|) as response signal in traditional impedancemetric-type NO2 sensor, various parameters including resistive component (Z′), capacitive reactance (Z″), |Z| and phase angle (Θ) extracted from impedance spectra were explored as the response signals for the present sensor. The sensors using all the extracted signals show excellent sensing performances in NO2 concentration range of 100−700 ppm. Compared with sensor using Z′ or |Z| response, the sensor using Z″ and Θ response can operate at higher frequencies and shows much better selectivity against CH4, CO2 and H2. Using Z″ as the response signal, the sensor exhibits a higher sensitivity to NO2 than that with other parameter as signal, because the response ΔZ′′ values vary linearly with respect to NO2 concentrations instead of logarithmic relation.

3D cell capture and sensing array electrode (3D ECCSA) under extremely low frequency electromagnetic fields (ELF-EMF)

Recently, many studies have shown that extremely low frequency electromagnetic fields (ELF-EMF) may lead to enhanced cell proliferation and inhibit the growth of specific cancer cells. In this study, 3D cell-based biosensors and an ELF-EMF device are integrated for real-time, non-invasive monitoring of single cell culture and measurement under ELF-EMF. MDA-MB-231 cells are cultured in a three-dimensional cell capture and sensing array electrode (3D ECCSA) chip under different intensities of ELF-EMF. A single cell is captured in the electrode for long-term impedance measurement (12 h). In this period, MDA-MB-231 cell goes through three different stages: cell capture, cell growth, and cell division, which can be measured by changes in impedance. Furthermore, the cellular impedance in ELF-EMF was found to be significantly lower than that of the group without ELF-EMF. In addition, an equivalent circuit was developed to determine the cellular resistance and capacitive reactance, and Maxwell’s mixture theory was used to determine the cell conductivity and permittivity to verify the effects of electromagnetic fields on cell membrane permeability and calcium ion exchange.