Capacitive Elements Research Articles

Detection of Lead and Environmental Parameters with Sulfur Film Modification of Screen Print Electrode

Environmental electrochemical sensors are an exciting field with a high volume of possibilities. Screen print electrodes have a tremendous advantage for environmental applications as they are 1) capable of performing laboratory and field measurements 2) allow a variety of surface science techniques and provide 3) an excellent outreach medium for students to learn about a variety of engineering and scientific disciplines. The use of redox-active (faradaic or “duck curve”) and non-redox (non-faradaic or capacitance) elements were used to detect lead and bicarbonate respectively using cyclic voltammetry. Aims of this project include the performance assessment of a screen print electrode with sulfur films treatments to detect these environmental compounds. This research education and outreach project summarizes efforts made to conduct and disseminate environmental electrochemistry to students in the New Brunswick area and Rutgers University. Remote and in-person learning labs were conducted to teach students fundamentals of electrochemistry and empower an underserved population to pursue science and engineering disciplines.

An Incremental Double Layer Capacitance of a Novel Ring-Disk Electrodes Array for Avidin/Strepavidin Sensing

Electric double layer (EDL) is established by ion redistribution at a solid-liquid interface. This ion redistribution electrically screens solid-surface charges and renders the interface to neutral. As a result, EDL is highly related to the surface potential, and a capacitor or constant phase element (CPE) is always employed to model the relationship between EDL and surface potential. According to this mechanism, diverse applications have been developed by controlling EDL via modulate potential fields or surface modifications. However, most of previous methods are sophisticated and hard to implemented as an in-situ monitoring method. To address this demand, we proposed a ring-disk electrode array (RDA) architecture to detect the changes of EDL capacitance between ring and disk electrode.Based on the proposed architecture, the surface potential will change while the biomolecular is immobilized onto to the vertical nanogap. This effect is verified by immobilizing different charged functional groups and the correlation between the surface potential and incremental-capacitance variance is also demonstrated. Based on this effect, the application for Avidin detection is implemented. The detectable range for Avidin measurement is from 100 fg/ml to 1 ng/ml.Based on this work, the incremental double-layer capacitance of a planar nanogap structure can provide a simple and reliable method for surface potential monitoring and can be used for different chemical and clinical examinations. Figure 1

Electrochemical Sensor Mediated Assessment of Carbonate Moieties in Soil Matrix

Carbon sequestration is a major global phenomenon that is particularly relevant now with the effect of climate change monitoring and regenerative agriculture. It refers to different practices that contribute to the absorption and storage of carbon in the soil. While the impact of sequestration of carbon is majorly from organic sources, the effect from soil inorganic carbon accumulation is not trivial especially in arid and semi-arid regions where the inorganic carbon (IC) share in sequestration is significant. Movement of Atmospheric Carbon Dioxide (CO2) into soil resources via photosynthesis and root respiration with the subsequent formation of bicarbonate in soil, which exists as bicarbonate in solution phase in groundwater sources or precipitates into CaCO3 in soil phase. Current soil carbon monitoring is either based on extensive soil sampling for analyzing in the laboratory or using proximal sensing methods, which are less accurate. Thus, implementation of novel soil sensors for accurate in-situ measurements could fundamentally improve soil carbon assessment and monitoring. Comparatively, the level and depth of assessing inorganic carbon in soil is significantly lower than that of soil organic carbon (SOC) monitoring. Electrochemistry as a transduction mode is highly viable in this regard due to its ease of applicability in various environments including the complex-soil matrix is a vital component that holds together the Earth’s ecosystem. The key mechanism of releasing the inorganic carbon relies on capturing the different pools that encompass the inorganic/ mineral carbon in soil including- carbonate ions in soil from Calcium (Calcite) which is the major pool of the IC in soil contributing to around 90% of this source and Magnesium (Dolomite). The other minor fraction that is present in the IC pool arises from Bicarbonates (HCO3-).In this sensor development study, we have designed a modified 3-electrode system which is functionalized with a correlated ion-capture film that is functional to changes in carbonate moieties in the soil electrolyte test system. Then this composite sensor was introduced into test soil setups with varying carbonate content to measure the sensor response- wherein, cyclic voltammetry (DC based) and Electrochemical Impedance Spectroscopy was used to determine signal output as a function of increasing dose. It was seen that the peak current around 0.4-0.5V on the positive axis was modulated to increase with carbonate content (% or ppm) and correspondingly- changes in the Rct (charge-transfer resistance) and Zw (Warburg impedance) along with the capacitive element shift was noticeable in the EIS spectra. The experimental cycle was performed using an in-house designed portable potentiostat device which was integrated into a probe head setup that could be inserted into soil for testing. The results from these experiments yielded linearity metrics from regression fits as R2 > 0.97 and measurable sensing range from 0.01% (100 ppm) to 1% (10,000 ppm). Therefore, a first-of-a-kind sensor system was developed for determining carbonate content in real soil samples using an electrochemical mode which will be subsequently tested in-field to survey field deployable and point-of-use capability of the system. Figure 1

Co-Designed Millimeter-Wave and Sub-6 GHz Antenna for 5G Smartphones

This letter proposes a co-designed millimeter-wave (mm-wave) and sub-6 GHz antenna system. The antenna system consists of four 28 GHz mm-wave arrays with reconfigurable radiation patterns and two sub-6 GHz antennas fed with two corner capacitive coupling elements (CCEs). Each corner CCE is formed by the connected ground planes of two mm-wave arrays in the shared-aperture configuration. The two CCEs are separately matched to cover two sub-6 GHz bands. Each mm-wave array consists of an active patch element and two parasitic patch elements loaded with PIN diodes, realizing 90° beam scanning range with two states of the PIN diodes. The measured results of the fabricated prototype show good agreement with the simulated ones. The prototyped mm-wave arrays cover the band 27.5–28.35 GHz, and each achieves 90° beam scanning at 28 GHz, with measured peak realized gain of 7.9 dBi. The CCE ports cover the two sub-6 GHz bands of 0.79–0.96 GHz and 1.7–5 GHz, with measured isolation of above 17 dB and 20 dB, respectively. The mm-wave band isolation is above 26 dB.

Distribution Capacitor Health Monitoring Based on the Disturbances of Element Breakdown Faults

As a common incipient fault for a compensation capacitor, the internal capacitor element breakdown fault (CEBF) causes slight changes in the steady-state voltage and current, which are difficult to accurately capture under the influence of measurement error. Therefore, to meet the demand for intelligent equipment maintenance by a smart grid, transient disturbances induced by a CEBF are used in this study to acquire element breakdown information for online monitoring of capacitor health. A transient response analysis of the CEBF in the time and frequency domains is used to establish the typical transient characteristics. Then, a multiple-kernel support vector machine algorithm is adopted to identify the transient disturbances. A method for determining the faulty capacitor unit is proposed based on the position of the waveform monitor. Under the assumption and statistics of the number of failed elements in a series group, a scheme for assessing the health condition is investigated. The proposed method can effectively obtain breakdown information to assess capacitor health with little influence of measurement error and background noise. The results of a theoretical analysis, computer simulation, lab experiment and field monitoring verify the effectiveness of the proposed method.

Building a surrogate model of a perfect electric conductor using polynomial chaos expansion and the characteristic mode analysis

A surrogate model for a perfect electric conductor plate is built by using the polynomial chaos expansion method. The plate is excited via four capacitive coupling elements for which the locations are determined by the analysis of the current distribution for each mode provided by the characteristic mode analysis. A numerical model based on the method of moments is then created to generate a database needed to build the surrogate model. Radiation patterns calculated by the surrogate model are compared with those given by the numerical model. The results show that the surrogate model can mimic the numerical model and it can be used to replace complex numerical models to save computation time and to alleviate the burden on the computation resources. Then, a sensitivity analysis is conducted to exhibit the effect of the parameter deviations on the overall antenna performance and to reveal the influential input parameters. The results of sensitivity analysis are used to reduce the complexity of the overall structure.

Modeling of the Signal Transmission of a Coaxial Connector With a Degraded Dielectric Layer in a Humid Environment

Radio frequency coaxial connectors are key components in circuits for signal transmission and directly influence the stability of communication systems. It is well known that connectors operating in harsh environments for extended periods are subject to physical degradation, which may lead to deterioration of signal integrity and overall communication quality. However, little work has been done with regard to connector dielectric degradation in humid environments. In this current work, the specific effects of connector dielectric degradation in humid environments on signal transmission are studied by theoretical and experimental analysis. Both a 3-D electromagnetic field model and an equivalent circuit model for connectors before and after degradation are developed in order to evaluate signal reflection and transmission loss. The results of these two models are compared and show good agreement. In addition, based on the material properties of the connector dielectric, the equivalent dielectric layer of a degraded connector is considered to consist of a double-layer dielectric structure composed of polytetrafluoroethylene (PTFE) and a layer of water film. The equivalent dielectric constant and equivalent loss tangent of the double-layer dielectric structure are calculated and analyzed. A corresponding equivalent circuit is developed consisting of an impedance network with resistance and capacitance elements in parallel. Experiment tests are conducted to validate the electromagnetic field model and the circuit model results. The results of this research provide a better understanding of the electrical characteristics of degraded connectors in humid environments and theoretical support for engineering applications.

APPLICATION OF REGRESSION ANALYSIS DURING THE ASSESSMENT PROCESS OF FACTOR IMPACT ON THE SENSITIVITY OF THE CAPACITIVE HUMIDITY SENSOR

In order to optimize the parameters of creating a moisture-sensitive layer of the capacitive humidity sensor, a multifactorial experiment plan was used in combination with regression analysis of the factor influence. Capacitive humidity sensors are made on a sitall substrate with size 0.7×0.9 mm, on the surface of which is applied a copper film, which forms the plates of the capacitive elements in the form of a meander with the appropriate geometry 7.85·10-2×150·10-6×1.2·10-6 m. Hygroscopic salt is a moisture-sensitive film that serves as a dielectric. Solutions of hygroscopic salt NaCl with concentrations 0.89 mol/l and 5.33 mol/l were used to create a moisture-sensitive film, which were applied to the surface of capacitive humidity sensors by spraying at a distance of 40–50 cm with thicknesses of 5.0 μm and 10.0 μm. Statistical processing of the results of the factor experiment by the Cochran test proved that the factor experiment is reproducible. Using the planning matrix of the full-factor experiment, a regression equation has been developed and on the basis of which it has been found that the concentration of salt solution used to create a moisture-sensitive layer significantly affects the sensitivity of the capacitive humidity sensor. According to Student criteria it has been established that all the coefficients of the regression equation are significant. Sensitivity has been chosen as criteria for parameters optimization of creation a moisture-sensitive layer of such a capacitive humidity sensor. The final regression equation on the scale of real factors makes it possible to optimize the parameters of creation a moisture-sensitive layer of the capacitive humidity sensor with the maximum values of the response function – “sensitivity”. It has been found that the highest sensitivity of 36.32 pF/% is provided by the following optimal parameters of the process of creating a moisture-sensitive layer: the concentration of salt solution, which serves as an adsorbent material, namely hygroscopic salt NaCl – 5.33 mol/l and thickness of moisture-sensitive layer 10.0 μm.

A Traveling Wave Based Method for Protection of Shunt Capacitor Bank

This paper proposes a traveling wave based scheme for wye-connected shunt capacitor bank protection. The proposed method provides high sensitivity and fast response, assisting in mitigating capacitor damage during internal cascading failure. The available protection schemes for capacitor bank use RMS values of voltage and current phasors for trip decision. Threshold selection is required in these methods which needs accurate estimation of equivalent capacitance of the bank. In addition, phasor being estimated from one-cycle running data window, such a method is slow. The proposed traveling wave based method identifies an internal fault in case of opposite polarities of traveling waves seen in the terminal voltage and current signals of the faulted phase. If the mid-point tapping is available in capacitor bank, the faulted half can be identified using the traveling wave of tap voltage. The magnitude of the traveling wave in terminal voltage reveals the number of failed capacitor elements. Such information assists in expediting maintenance. The performance of the proposed method is tested using PSCAD/EMTDC simulation data for various situations, including internal short circuit, external, and identical faults in the shunt capacitor bank. Comparative analysis highlights its higher sensitivity and better accuracy in comparison to available protection methods.

Dual-coil micro-impedance resonance oil contaminant detection sensor based on microfluidic chip

A dual-coil micro-impedance resonant sensor for on-line detection and impurity analysis of mechanical oil systems was designed in this experiment. Through the design of the double coil, inductance detection and capacitance detection are realized on the same chip. Furthermore, the resonant circuit formed by the sensor plus an inductive element and a capacitive element further improves the detection sensitivity of the sensor. This paper establishes a resonant circuit model and conducts theoretical analysis. It verifies the accuracy of theoretical analysis by comparing the micro-impedance resonant sensor with the sensor without micro-impedance resonance. It is confirmed that the resonant sensor has better detection sensitivity. The experimental results determine the frequency characteristics and the optimal frequency of the resonant sensor. This paper has a guiding role in the design of such sensors, and providing technical support for the development of online detection.

Partial discharge calibrator of a cavity inside high-voltage insulator

Abstract This article displayed the method of partial discharge (PD) measurement in high-voltage insulator and calibrating the effective element (capacitor) to enhance the PD signal. The cavity shapes were plate–plate, cylindrical and spherical inside the solid insulator. The proposed system enables from detecting the reverse and main discharge, respectively, through the rise and tail time of the pulses. PD that took place was bounded with internal cavities. Proteus simulator and Matlab simulation models were used to measure and display the PD signal. The results showed PD-calibrated waveforms and the voltage values across the cavity (V c). Finally, this work concluded that the spherical cavity shape gave a higher value of the calibrated capacitor and lower voltage across the cavity (V c) for both models.

Pattern Reconstruction for Antennas with Characteristic Mode Analysis and Surrogate Model

A novel approach is applied to obtain a desired pattern for a perfect electric plate with two ports. The location of ports is decided with the help of characteristic mode analysis. Two capacitive coupling elements are chosen to be used as excitation. The magnitude and phase of each excitation are obtained by the Bayesian inference method. In order to avoid complexity of computational design, a surrogate model, which is based on polynomial chaos expansion, is built. The surrogate model is ensured to mimic the computational model over 90%. Then, the desired pattern is compared with the synthesized one, and it is seen that the two patterns fit very well to each other and the correlation between the two patterns is above 0.9.

Efficient Static-Driven Integration for Step-Function Transient Simulation

Step-function excitations are convenient abstractions for circuit turn on/off and for switching activities in general. However, they are ill-handled by SPICE-derived circuit simulators that employ implicit integration approximations and substitute steep ramps for steps. An ACES-derived explicit integration method efficiently handles step-functions, manages potential instability, and converges to the steady state. The resulting circuit simulator can be employed to find an initial state size and excursion-limited accuracy control. It also is able to accommodate resistance, capacitance, inductance, and nonlinear elements efficiently and accurately.

Parameter Extraction Technique for Evaluation of Inductive and Capacitive Elements of Three-Winding Coupled Inductor

Wide-bandgap devices have enabled miniaturization of magnetic components to enhance the power density of the converter. However, parasitic components become dominant at higher switching frequencies that actuate unwanted electromagnetic interference issues. Therefore, it is critical to model and evaluate them in compact magnetic structures. Since multiwinding coupled inductive structures are essential part of multiphase converters, this article introduces a measurement method to compute the parasitic elements of a three-winding coupled inductor. Results of the proposed method are verified by measuring the high-frequency emissions of the high-step-up converter with two inductor structures. Both inductors had similar inductances but different physical dimensions. With application of the proposed measurement methodology, parasitic capacitances of both inductors were computed. Results showed that one inductor structure has higher parasitic capacitance than the other. Since high-frequency emissions of the converter directly depend on the parasitic capacitance of the inductor structure, the emission profile of the converter showed that the converter indeed had lower noise peaks when the inductor with lower capacitance was employed. Hence, these results validate the capacitance trend as predicted by the proposed modeling technique. This method can be employed to any multiwinding coupled inductor to compute its parasitics to optimize the required electromagnetic interference filters.

Effect of irradiation on pyroelectric and electrocaloric parameters in lead-free relaxor ferroelectric ceramic

Ferroelectric materials have a renaissance due to various photosensitive characteristics. In this study, temperature-dependent dielectric, impedance, and ferroelectric measurements were carried out on lead-free Ba0.6(Bi0.5Li0.5)0.4TiO3 (BBLT) ferroelectric ceramic under the dark and exposure of monochromatic 405 nm light conditions. Profound analysis of complex impedance spectroscopy shows a noticeable reduction in bulk capacitance, relaxation time, and constant phase element parameters under illuminated conditions. Relevant phenomenological approaches towards modified Cole−Cole models confirm that the light induces photogenerated nonequilibrium charge carriers. Thus, the trapped charges alter the internal electric field distribution energy. Under illumination, the enhanced polarization and corresponding pyroelectric coefficient enhanced by 40 % and ~260 % at 5 Hz and 10 Hz, respectively, at 20 ℃ were observed. The cross-coupled Electrocaloric (EC) parameters ∆T and ∆S enhanced 600 % and 571 % at 10 Hz, respectively, and 219 % and 218 %, at 5 Hz respectively at 20 ℃ under illumination. This study provides a comprehensive understanding and new insights into the light-dependent dielectric, ferroelectric, pyroelectric and electrocaloric mechanisms in BBLT electroceramics, which encourages the design of modern thermal sensor devices.

Analysis of light and no‐load operation of a 300 kW resonant single active bridge based on 3.3 kV SiC‐devices

The resonant single active bridge topology (R-SAB) operated in the half-cycle discontinuous current mode (HC-DCM) is a very attractive solution due to its high efficiency, low complexity and fixed voltage transfer ratio (DCX). However, as expected for a series-resonant converter (SRC), its DCX operation depends on the resonant tank circuit-parameters, parasitic capacitive elements and output load. Specially, at light and no-load operation, when the system is extremely underdamped, it may present a large output overvoltage due to resonance interactions. This is of prime importance for converters using medium voltage (MV) SiC-MOSFETs, which feature significant output capacitances that can lead to voltage breakdown of the rectifier semiconductors. Therefore, the supposed fixed-voltage transfer ratio is not entirely valid and deserves a proper understanding due its criticality. This paper reviews the subject, clarifying its root cause and its multifactorial dependencies. Moreover, it provides a simple solution based on a variable dead-time with fixed magnetizing current experimentally verified with a 300kW/1.8kV R-SAB prototype implemented with MV SiC-devices.

Design of an Integrated Power Module for Silicon Carbide MOSFET with Self-Compensation of the Magnetic Field

Compactness, efficiency, and light weight are the key topics in the design of power conversion systems for transportation applications. This demand is achievable by using wide band gap devices such as SiC devices, characterized by the high switching speed and low on-resistance. However, this trend imposes new challenges and the effect of parasitic elements of power package during switching transient becomes significant. Hence, new packaging solutions should be investigated for addressing this concern. This paper presents a new multichip power module architecture, where its design considering capacitive and inductive stray elements is carried out. Using Ansys Q3D Extractor, electromagnetic simulations are achieved to extract the inductive and capacitive parasitic element of one leg of a three-phase inverter.

The Implicit McMillan degree and network descriptions

Abstract The paper addresses the problem of evaluating the Implicit McMillan degree$\delta{m}$ of $W^{-1}(s)$, where $W^{-1}(s)$ denotes the transfer function of a passive $RLC$ electrical network.1 The Implicit McMillan degree$\delta{m}$ specifies the minimum number of dynamic elements needed to completely characterize the passive $RLC$ network, i.e. an electrical network that contains only passive elements (capacitors, inductors and resistors) and associates it with the rank properties of the passive element matrices. A fact that in the circuit literature is intuitively accepted but not rigorously proved is that this degree must be equal to the minimum number of independent dynamical elements in the network Livada (2017, Implicit network descriptions of RLC networks and the problem of re engineering. Ph.D. Thesis, City, University of London) and Leventides et al. (2014, McMillan degree of impedance, admittance functions of RLC networks. In 21st International Symposium on Mathematical Theory of Networks and Systems. The Netherlands: Groningen). In this paper, we investigate this finding, showing that the maximum possible Implicit McMillan degree$\delta{m}$ of such networks is given by $rankL+rankC$ and that this value is reached when certain necessary and sufficient conditions are satisfied.1

Fifth-Order Generalized Integrator for a Double-Stage Single-Phase Grid-Interfaced Photovoltaic Supply System

This paper presents a fifth-order generalized integrator (FOGI) as an orthogonal signal generator (OSG) to obtain a grid synchronization signal for a double-stage single-phase grid-interfaced photovoltaic supply system (GIPVSS). The proposed GIPVSS consists of a single-ended primary inductor converter (SEPIC) and a H-bridge voltage source converter (HBVSC) to transfer solar power to the grid system. The SEPIC controls maximum power delivery (MPD) from the Photovoltaic (PV) array and feeds that power to the grid via an HBVSC. In this study, all energy storage elements (inductors and capacitors) of SEPIC are considered with their effective series resistance (ESR). The dynamic modeling of SEPIC is obtained using a small signal analysis. The control of VSC allows harmonics’ mitigation and power factor improvements. A FOGI and a second-order adaptive filtering approach are used in controling VSC. The FOGI is used to obtain a grid synchronization signal from sensed grid voltage under disturbances. The second-order adaptive filtering approach is used to obtain an active load current component. The comparative analysis of FOGI with other reported algorithms is carried out under harmonics in sensed grid voltage. The effectiveness of the proposed system and its control is validated in a laboratory prototype using a Launch Pad TMS320F28379D digital signal processor (DSP).

Humidity response of a capacitive sensor based on auxeticity of carbon nanotube-paper composites

Auxetic materials showing a negative Poisson’s ratio can offer unusual sensing capabilities due to drastic percolation changes. This study presents the capacitive response of wet-fractured carbon nanotube paper composites in exposure to humidity. A strained composite strip is fractured to produce numerous cantilevers consisting of cellulose fibers coated with carbon nanotubes. During stretching, the thin composite buckles in the out-of-plane direction, which causes auxetic behavior to generate the radially structured electrodes. The crossbar junctions forming among the fractured electrodes significantly increase capacitance and its response to humidity as a function of sensor widths. The molecular junctions switch electric characteristics between predominantly resistive- and capacitive elements. The resulting capacitive response is characterized for humidity sensing without the need for an additional absorption medium. The normalized capacitance change (ΔC/C0) exhibits a sensitivity of 0.225 within the range of 40 ∼ 80% relative humidity. The novel auxetic behavior of a water-printed paper-based nanocomposite paves the way for inexpensive humidity and sweat sensors.