Calculation Of Impedance Research Articles

A novel model for calculating the impedance of arbitrarily-shaped coils with perpendicular to the planar medium

Some studies have shown that coils placed perpendicular to conductors have excellent detection effect for specific defects in eddy-current testing (ECT), where the impedance is an important parameter. The impedance calculation for perpendicular coil is more complex than that for parallel coil, and currently the main focus is on the impedance analysis of circular and rectangular coils. In this paper, a closed formula for the impedance of a coil with arbitrary-shape perpendicular to the conductor is given based on the second order vector position method. In the proposed model, a novel shape and position function is defined to extend the coil application to arbitrary cross-sectional shapes. Meanwhile, experimental comparisons are conducted to evaluate the impedance of various coils on an aluminum plate. The results illustrated that the experimental values are in perfect agreement with the calculated ones. Therefore, the proposed model can provide guidance for the impedance calculation of arbitrarily-shaped coils in eddy current testing.

Improved self-consistency and oxygen reduction activity of CaFe2O4 for protonic ceramic fuel cell by porous NiO-foam support

Considerable efforts have been made in the past several decades to search the cheap metal-oxides electrocatalysts with superior electrical properties including ionic and electronic for electrochemical energy devices. In this work, simple orthorhombic structured CaFe2O4 nano-particles were embedded on a porous Ni-foam by spin coating method for the application of air electrode for protonic ceramic fuel cells (PCFCs), which provides high oxygen reduction activity than using traditional processes. CaFe2O4 coated Ni-foam cathode shows very small area-specific-resistance (ASR) of ≤0.2 Ωcm2and fuel cell device assembled by CaFe2O4 coated Ni-foam cathode over ceramic BaZr0.8Y0.2O3 (BZY) electrolyte exhibited a peak power density (PPD) of 612 mW cm−2 when operating at 500°C. The porous Ni-foam support superficially improves the electrical and gas diffusion capabilities along with ionic transport properties of CaFe2O4 by narrowing the bandgap to effectively facilitating small polaron hopping energy of valence electrons. However, various spectroscopic measurements such as electrochemical impedance, X-ray photoelectron, thermogravimetric analysis, and Density Functional Theory (DFT) calculations were employed to understand the improved ORR electrocatalyst function of CaFe2O4 with Ni-foam support as three-dimensional heterostructure composite cathode. The results can further help to develop functional cobalt-free electro-catalysts for low temperature-PCFCs and other related applications.

A numerical model with high-accuracy and high-efficiency for the soil dynamic impedance of pile groups under vertical vibration

This paper develops a novel numerical model for the calculation of dynamic impedance of soil considering end-bearing pile groups under vertical vibration. The soil layer is treated as a linear viscoelastic material with hysteretic damping. The vertical displacement is assumed to be uniform in each individual pile in the groups at the same embedment depth. Using separation of variables and applying proper boundary conditions at the surface and rigid bedrock, the governing equation of soil layer in three-dimensional (3D) is first transformed into a two-dimensional (2D) Helmholtz equation in xy plane, where the solution in the vertical direction is obtained analytically. To solve this problem efficiently and accurately, the whole 2D unbounded soil is then divided into a finite interior domain and an infinite exterior domain. The finite domain is discretized using the finite element method (FEM) while an exact circular artificial boundary condition (ABC) is developed to model the infinite domain. Finally, the effect of pile group interaction on the dynamic impedance of soil is investigated considering various factors, e.g., dimensionless frequency, pile number, pile slenderness ratio and relative distance between piles.

Calculation and Optimization of Resistive Wall and RF Cavity Impedance in Medium Energy Diffraction Limit Storage Ring

Calculation and Optimization of Resistive Wall and RF Cavity Impedance in Medium Energy Diffraction Limit Storage Ring

Calculation and analysis of plasma impedance during closing process of laser‐triggered vacuum switch

The plasma characteristics of laser‐triggered vacuum switch (LTVS) have significant effects on the output characteristics of a pulsed power system during closing process. The plasma impedance can link the microscopic properties of plasma and the macroscopic electrical parameters effectively. In this paper, the mathematic representations of plasma impedance are calculated theoretically with the equivalent circuit. External circuit inductance and resistance are calculated by means of ANSYS software and discharge time constant, respectively. Furthermore, the current and voltage experimental waveforms during closing process are analyzed by fitting piecewise linear functions in MATLAB. The plasma impedance can be calculated based on the above conditions. The calculation results show that the plasma resistance reduces with time exponentially, which is caused by an exponential increase in electron density during closing process. In addition, the plasma inductance shows an overall trend of decreasing over time, but there are fluctuations.

Impedance minimization of the CERN Super Proton Synchrotron cavities using the generalized coupled S -parameter method

In the context of the Large Hadron Collider (LHC) injector upgrade, components with high contribution to the beam coupling impedance of the injector chain have to be identified and optimized to ensure the delivery of high-intensity proton beams to the LHC. The Super Proton Synchrotron (SPS) is the last accelerator in the LHC injector chain. In the existing design, the longitudinal beam coupling impedance of the SPS cavities limits the increase of the beam intensity in the SPS ring. Since the 200 MHz traveling wave cavities are one of the main contributors to the overall beam coupling budget of the SPS machine, different types of higher-order mode (HOM) couplers are used in the long 33-cell and 44-cell cavities for the damping of various HOMs. The location of the HOM couplers in the cavity, as well as their shape, affects the damping of HOMs. Finding a suitable arrangement of the HOM couplers requires solving a discrete optimization problem. The repetitive calculation of the beam coupling impedance by the conventional time-domain wakefield solvers in the optimization is hindered by the large size of the SPS cavities. The generalized coupled $S$-parameter method is a domain decomposition method for the calculation of the $S$ parameters and beam coupling impedance of large structures. In this paper, this method is employed to calculate the beam coupling impedance of the SPS cavities. Then, an optimization method is proposed to find an optimal arrangement of the HOM couplers in the cavities. The article presents the geometrical details of the SPS cavities, a short description of the generalized coupled $S$-parameter method, and a discrete optimization method applied to the SPS cavities.

Estimation of zero sequence impedance in power transformers using 2D and 3D FEM

This paper describes calculation of zero sequence impedance in three phase, three leg core type power transformers using 2D and 3D finite element method (FEM) calculation on example of 100 MVA power transformer. Paper also describes how winding connection and arrangement affects the size and calculation of zero sequence impedance.

Application of the Conformal Mapping Method for the Calculation of the Characteristic Impedance of the Floquet Channel for the Ultrawideband Cophased Antenna Array Consisting of TEM Horns

Application of the Conformal Mapping Method for the Calculation of the Characteristic Impedance of the Floquet Channel for the Ultrawideband Cophased Antenna Array Consisting of TEM Horns

Analysis and optimization of leakage impedance in a transformer with additional winding: A numerical and experimental study

Transformers are one of the most important elements of electrical power systems. In several conditions, the same transformer is connected to many different networks with different voltage levels and the replacement of the transformer is one of the most difficult tasks for the power suppliers. Tap winding transformer can be used to overcome the problems of the variable primary or secondary voltages. However, tap winding positions and type significantly affect the overall leakage impedance and it is one of the major concerns for the tap winding transformer designers. In this paper, the tap winding transformer distance was optimized with additional tap winding on the high voltage winding side. To optimize and calculate the leakage impedance in the tap winding transformers with three different voltage levels, finite element analysis was used. The prototype tap winding transformer was manufactured with the help of the finite element method. The difference between the short-circuit experimental test and the finite element method result was less than 1%. The experimental results show that optimal calculation of the leakage impedance in the tap winding transformer can be achieved with help of the finite element analysis.

Highly Integrated Online Multi-Channel Electrochemical Impedance Spectroscopy Measurement Device for Fuel Cell Stack

Electrochemical impedance spectroscopy (EIS) can provide information about the internal state of fuel cells, which makes EIS an important tool for fuel cell fault diagnosis. However, high cost, large volume, and poor scalability are limitations of existing EIS measurement equipment. In this study, a multi-channel online fuel cell EIS measurement device was designed. In this device, based on multi-phase interleaved Boost topology and average current control, an excitation source, which can output 1~500 Hz, 10 A sinusoidal excitation current was designed and verified by model simulation. Then, based on the quadrature vector digital lock-in amplifier (DLIA) algorithm, an impedance measuring module that can achieve precise online impedance measurement and calculation was designed. A prototype was then built for the experiment. According to the experiment test, the amplitude error of the excitation source is less than 1.8%, and the frequency error is less than 0.3%. Compared with the reference data, the impedance measured by the prototype has a modulus error of less than 3.5% and a phase angle error of less than 1.5°. Moreover, the waveform control and impedance extraction function of the EIS measurement device is implemented on an embedded controller, which can cut the price and reduce the volume.

Study on the estimation of harmonic impedance based on Bayesian optimized Gaussian process regression

System harmonic impedance is a key parameter in the evaluation of harmonic emission level and harmonic responsibility allocation. In order to solve the problem of calculating the harmonic impedance when background harmonics are different, a method of calculating the harmonic impedance based on Bayesian optimized Gaussian process regression (O-GPR) is presented. The harmonic impedance calculation method is based on the harmonic voltage and harmonic current obtained at the point of common coupling (PCC), and the Bayesian optimization of the Gaussian process regression is used to calculate the harmonic impedance of the system. Considering the influence of background harmonics, the harmonic equivalent models with non-Gaussian distribution background harmonics and Gaussian distribution background harmonics are built in the simulation analysis. The accuracy of this method under different background harmonics is analyzed, and its robustness is evaluated by error comparative analysis. Case analysis further verifies the effectiveness of the method. Also, the method is evaluated through indicators such as mean value, standard deviation and root mean square error. It provides ideas for practical engineering applications.

Research on Calculation of Rail Self-Impedance of Track Circuit Based on Partial Element Equivalent Circuit

The self-impedance of the steel rail, as the signal transmission medium in the electrified railway track circuit, has a direct impact on the track circuit’s transmission performance. The finite element method is the most common method for calculating rail impedance, although it has a number of drawbacks, including a complicated model, a long computation time, and poor accuracy. The partial element equivalent circuit (PEEC) approach is used in this paper to provide a method for determining rail self-impedance. Firstly, the rail equivalent method is determined by analyzing the physical model of the rail. Considering the skin effect, the PEEC model of the rail is established. The internal impedance of the rail can be obtained by solving the equivalent circuit. The external impedance considering the influence of the earth is calculated by the Carson impedance calculation formula, which is processed by the segmented linear approximation method. The rail’s self-impedance is determined using the two procedures together. Finally, the actual measurement data verified the PEEC method to calculate the rail impedance. Compared with the finite element method (FEM), the calculation accuracy of the PEEC method is higher. The current frequency, the height of the rail from the ground, and the earth’s conductivity impact on the rail’s self-impedance are analyzed. The results show that the PEEC technique can be used to calculate the rail’s self-impedance and that the impact of current frequency, rail height above the ground, and ground conductivity on the rail’s self-impedance may be accurately represented. The self-impedance computation of the track circuit provides a theoretical basis.

Internal impedance analysis of rectangular conductors at high frequencies

This paper presents the internal impedance analysis of rectangular conductors using analytical calculations. A novel 2D analytical formula is presented using a variational method. And its impedance calculation is compared with other analytical formulas with the format of sum of series for internal impedances calculations of rectangular conductors at high frequencies. It is shown that the novel analytical formula for internal impedance calculation has excellent accuracy despite its simple and closed form function. Dirichlet boundary condition is used by applying zero magnetic vector potential on the edges of rectangular conductor for the analytical calculations of internal impedance. The internal inductance and resistance are calculated at different frequencies between 1 MHz and 1000 MHz. The accuracy and simplicity of different analytical formulas for the internal impedance of rectangular conductors and equivalent circular conductors are compared.

Precision Calculations of the Characteristic Impedance of Complex Coaxial Waveguides Used in Wideband Thermal Converters of AC Voltage and Current

Precision Calculations of the Characteristic Impedance of Complex Coaxial Waveguides Used in Wideband Thermal Converters of AC Voltage and Current

Characteristics of ULF Magnetic Fields in the 3D Inhomogeneous Earth‐Ionosphere Waveguide

AbstractWe develop an algorithm for calculating the characteristics of the magnetic field of signals in the frequency range of (0.1–20) Hz in the horizontally and vertically inhomogeneous spherical Earth‐ionosphere waveguide. This algorithm involves calculations of the surface impedance of an inhomogeneous ionosphere. The frequency dependences of the amplitude, phase and polarization of the magnetic field generated by a horizontal magnetic dipole were analyzed. It is shown that the horizontal inhomogeneity of the Earth‐ionosphere waveguide can significantly affect the frequency dependence of the amplitude and polarization of the magnetic field, increasing the degree of circular polarization. The horizontal inhomogeneity only slightly influences the results in daytime conditions. The most noticeable difference in the amplitude dependences of the magnetic components and large phase shifts (up to 40°) are observed when the terminator passes through the geodetic line connecting the source and receiver, and in the presence of sporadic layers with a horizontally inhomogeneous structure along the low‐frequency wave propagation path. We compare the calculation results with the magnetic pulsations recorded at Nurmijarvi station during the 2001 campaigns of Kola Peninsula ultra low frequency emitter operation. The obtained results make it possible to qualitatively explain peculiarities of the amplitude and polarization spectra of the artificial magnetic signals recorded in this campaigns that are not explained within the framework of the flat homogeneous waveguide model.

Protection of Microgrid Interconnection Lines Using Distance Relay With Residual Voltage Compensations

Protection of microgrids at the Point of Interconnection (POI) is a challenging task. Particularly, single-line-to-ground (SLG) faults on interconnection lines are difficult to detect using the fault current detection relays if the microgrid is ungrounded at utility side of its interconnection transformer; such microgrid contributes very low fault current, which disappears once the utility feeder breaker opens. Other common schemes for protection of microgrid interconnection line against SLG faults include Direct Transfer Trip (DTT) and over-voltage relay (59G). The main challenges associated with these methods are installation and maintenance costs of high-speed communication system, sensitivity of relay settings, and delayed fault clearing time due to selectivity requirements. To address such concerns, this paper proposes the use of a distance relay at the microgrid/LV side of the interconnection transformer to provide protection against SLG faults on the interconnection line at the utility/HV side. The designed distance relay executes an enhanced apparent impedance calculation using residual voltage compensation to correctly detect the fault, properly measure the fault location, and timely isolate the fault. In this paper, various scenarios are analyzed using ASPEN and PSCAD simulation tools to demonstrate the effectiveness of the proposed method for protecting the microgrid interconnection line under different fault scenarios.

A Line Impedance Calculator Based on a G3 PLC Modem Platform

Power line communication (PLC) is one of the most today used technologies for both automatic meter reading and many other smart grid applications. In this framework, a characterization of the electrical network in the PLC frequency range is needed in terms of impedance measurement and received signal level. This can allow choosing the most suitable and less noisy frequency ranges for PLC transmission. Usually, these characterization measurements are performed with dedicated instrumentation and in the absence of mains voltage. This article wants to propose an alternative solution, which allows these kinds of measurements to be performed using electronic boards currently used as on-field applications, such as smart meters. To this aim, an innovative measurement tool is proposed, which does not need a specific characterization signal to be injected because it uses the preamble of a generic PLC transmission. Moreover, the impedance calculation is performed using an FFT analysis, which does not require high computational capabilities. These features allowed the proposed tool to be implemented using a G3-PLC transceiver, embedded in many commercial smart meters, and low-cost additional hardware. This article shows how the proposed system correctly measures the PLC impedance on CENELEC A, B, and FCC frequency ranges.

Effect of sensor shape on the equivalent impedance signature for the detection of defects using eddy current testing

Eddy current testing is widely used for non-destructive evaluation of electrically conductive materials. This technique was recognized to be quite sensitive to defects affecting the geometry of a part or its electromagnetic properties, such as inclusions, cracks or corrosion. It is easy to implement, sturdy in the context of industrial applications and relatively inexpensive. Due to the growing need for reliability, the development of new eddy current systems is required. This work was dedicated to the design of new shapes of probes with the aim to increase detection capability. The objective is to assess how probe design can improve imperfection presence signature in a tested specimen. The methodology used is based on finite element simulation of B-scan process and calculation of the equivalent impedance seen across the terminals of the probe. Monitoring variations of this impedance for both the flawless control case and that with the presence of a defect was performed. Seven different shapes of probes were studied. It was found that the signature associated to the variation undergone by the impedance depends hugely on the probe geometry.

An analytical form for the correction factor for the vibrator antenna input impedance calculation by the equivalent long line method

An analytical form for the correction factor for the vibrator antenna input impedance calculation by the equivalent long line method

Efficient DC and AC Impedance Calculation for Arbitrary-Shape and Multilayer PDN Using Boundary Integration

This article presents an efficient methodology based on boundary integration to calculate the dc and ac impedance of power distribution networks (PDNs) for arbitrary-shape and multilayer printed circuit boards (PCBs). The proposed method adopts a boundary element method to extract inductances for the arbitrary parallel-plane shapes. Subsequently, the equivalent circuit formed by the via inductances and plane capacitances is solved using the node voltage method. By merging the parallel and serial inductances and simplifying the equivalent circuit, the computation time can be significantly reduced for a large number of vias and layers. This matrix manipulation strategy can be applied to various PCB structures without human intervention or commercial circuit solvers. Moreover, a contour integral method is employed to calculate the dc resistances for arbitrary shape and multilayer PDNs. Therefore, the wideband PDN impedance from dc to ac frequencies can be efficiently calculated through 1-D boundary integration, which can be performed more quickly than full-wave simulations. The proposed method can aid in the development of electronic design automation tools for PDN design.