Coaxial Coils Research Articles

Study on the Influence of Coil Placement on Pulsed Eddy Current Testing

The pipeline system of plant is installed with an insulation layer on the outer wall of the pipeline. Currently, the primary methods of detecting pipeline system is ultrasound and uradiographic testing, which require the removal of the outside layer before testing. As a result, detecting time extends, and labor costs increase, increase the risk of accidental exposure. Applying the PEC technique for steam pipelines can eliminate the disassembly of insulation and achieve non-stop online screening. The defects testing by coil placement is an essential indicator of the PEC technique, which is the main influence factor of PEC accuracy. The article intensifies the modeling and simulation of the pipelines by applying Ansys Maxwell and designs coaxial and vertical detection coils to simulate the detection capability of PEC on flat bottom defects in case of consistency in the lift-off distance, materials, and other conditions. It selects nuclear power plant sample pipes for coaxial and vertical PEC testing. Recording the test result of PEC and UT methods, and the effects of two coil placement methods on PECT are compared. Finally, the study proposes development trends.

Determination of Electrodynamic Forces between Coaxial Coil Turns with Current of Various Configuration

Determination of electrodynamic forces, as may be required for various practical purposes, is based on known calculation recommendations for mutual inductance coefficients, including the calculation methods with special functions, like complete elliptic integrals of the 1st and the 2nd kind, as well as spherical Legendre functions of the 2nd kind with half-integer index [1–5]. Some examples of practical tasks requiring these calculations are the assessments of mutual inductances in non-contact chargers, as well as the assessments of electrodynamic interactions in the windings of transformers, inductors, various solenoid-based loading devices, electric drives, etc. These applications are discussed in numerous publications and guides, e.g. [6–9].

Electromagnetic Excitation of Coaxially-Coiled Constantan Wires by High-Power, High-Voltage, Microsecond Pulses

This paper is mostly based on our presentation given at the 23rd International Conference on Condensed Matter Nuclear Science (ICCF23) held at Xiamen University (XMU)-PRC on June 9-11, 2021. Upon the suggestion of the Conference Organizers, we added a detailed explanation of our procedures; moreover, we included the latest results and data from our recently published papers. In the framework of LENR-AHE (Low Energy Nuclear Reaction - Anomalous Heat Effects) studies, since 2021, we have been focused on innovative, low-cost materials instead of the usual, precious metal palladium. We found that the Cu-Ni alloy, known as Constantan (also used for J-type thermocouple construction), has the peculiarity of being able to easily dissociate H2 (or D2) from molecular to an atomic state. While the catalytic feature appears at a rather low temperature (150 ◦C), Constantan is also able to store atomic hydrogen within its lattice and/or at surfaces, up to temperature of 700-800 ◦C, and in a wide range of pressures. Thanks to our long experience (since 1994) with wires, we designed various experiments that take advantage of such specific shapes, namely in terms of electromigration of absorbed and adsorbed H, under a suitable longitudinal electric field (0.4-2.5 V/cm), DC and/or pulsed. In 1995 we got noticeable results using Pd wires in electrolytic environments (D2O) at mild temperatures (40-60 ◦C). Later on, in some experiments, we used even gaseous environments at high temperatures (up to 700-800 ◦C). The main problem of Pd was its large brittleness after H or D absorption. Moreover, we experimentally reconfirmed that one of the key conditions to induce AHE is the “flux” of H moving inside its lattice (longitudinal) or through the surface (transversal). Pioneers of transversal flux were G. C. Fralick-NASA [1]; M. McKubre-SRI [2]; Y. Iwamura-Mitsubishi [3], [4], [5]; Y. Arata-Osaka Univ [6]; F. Celani-INFN [7]. We focused mainly on longitudinal flux (following also the theoretical models developed by G. Preparata-Milan Univ. [8], although some of our unconventional electrolytic experiments (1995-1998) had both. In any case, apart from the initial state (the situation of intrinsic hydrogen concentration gradients), the flux needs external energy to be continuously activated. Based on our own experiences since April 1989, AHE are due to non-equilibrium conditions, i.e., they need continuous stimulation, usually energy consuming, apart from some specific (but delicate) geometric set-ups (such as the Capuchin knot, which we began testing in 2018, in some of our geometric arrangements where local thermal gradients were extremely large: > 100 ◦C/mm). Recently, we developed an unconventional geometry of the electrode we aimed to use, and at almost the same time, longitudinal and transversal flux at high temperatures in gaseous environments: our goal was to minimize extra energy added, to maximize the AHE and keep it operative for as long as possible. We report here on procedures to enable flux by high power electric pulsing with both related problematics and peculiar advantages, some unexpected. The core of the reactor is arranged as a reversed coaxial coil with inner electrode made by a Fe tube, which we described beginning in 2019 at ICCF22.

Электродинамические силы между соосными плоскими катушками круговой формы

Object and purpose of research. Non-contact power transfer to various marine facilities. Subject matter and methods. The study relied on the methods of theoretical electric engineering. Main results. This paper gives analytical estimates for electrodynamic forces acting on inductively-coupled coaxial flat coils of circular shape. Conclusion. The study yielded the expressions for the electrodynamic forces in inductively coupled circular coils interfaced so as to perform non-contact power transfer.

A flexible MRI coil based on a cable conductor and applied to knee imaging

Flexible radiofrequency coils for magnetic resonance imaging (MRI) have garnered attention in research and industrial communities because they provide improved accessibility and performance and can accommodate a range of anatomic postures. Most recent flexible coil developments involve customized conductors or substrate materials and/or target applications at 3 T or above. In contrast, we set out to design a flexible coil based on an off-the-shelf conductor that is suitable for operation at 0.55 T (23.55 MHz). Signal-to-noise ratio (SNR) degradation can occur in such an environment because the resistance of the coil conductor can be significant with respect to the sample. We found that resonating a commercially available RG-223 coaxial cable shield with a lumped capacitor while the inner conductor remained electrically floating gave rise to a highly effective “cable coil.” A 10-cm diameter cable coil was flexible enough to wrap around the knee, an application that can benefit from flexible coils, and had similar conductor loss and SNR as a standard-of-reference rigid copper coil. A two-channel cable coil array also provided good SNR robustness against geometric variability, outperforming a two-channel coaxial coil array by 26 and 16% when the elements were overlapped by 20–40% or gapped by 30–50%, respectively. A 6-channel cable coil array was constructed for 0.55 T knee imaging. Incidental cartilage and bone pathologies were clearly delineated in T1- and T2-weighted turbo spin echo images acquired in 3–4 min with the proposed coil, suggesting that clinical quality knee imaging is feasible in an acceptable examination timeframe. Correcting for T1, the SNR measured with the cable coil was approximately threefold lower than that measured with a 1.5 T state-of-the-art 18-channel coil, which is expected given the threefold difference in main magnetic field strength. This result suggests that the 0.55 T cable coil conductor loss does not deleteriously impact SNR, which might be anticipated at low field.

Determination of Radial Forces Acting Between Coaxial Coils Located in the Same Plane

The electrodynamic forces acting between coaxial turns with current are estimated for the case when the turns belong to different layers in a multilayer coil, which are arranged in the same way. Expressions for the radial components of electrodynamic forces acting on a concentric outer turn are given. The suggested expressions are verified for consistency with the result obtained for the mutual inductance gradient in the radial direction, known from [1]. The expressions for tensile forces in the case of thin-layer disk coils based on their determination in terms of the inductance derivative with respect to the average radius are compared in two versions: with reference to Wheeler's approximating formulas for inductance, one of which is written in [2], and the other in [3]. The article may be useful for specialists dealing with evaluation of inductances and electrodynamic forces in the live parts of electrical systems.

Analytical model for calculation of the magnetic field of triaxial uniform coils in magnetically shielded cylinder

An analytical model to calculate the magnetic field of triaxial uniform coils inside magnetically shielded cylinders (MSCs) composed of high-permeability materials is proposed. The proposed model offers two major advantages over existing methods. First, the model is not limited to the research on coaxial circular coils, but also can be used to analyze the magnetic field characteristics of saddle coils inside MSCs. Second, based on Green’s function expansion and the ferromagnetic boundary conditions, the image method is introduced to consider the reflection effect of the MSC end cap on the coil, thus enabling the coupling effect between the coil and the MSC to be analyzed. To verify the model’s correctness, simulations and experiments are performed separately. With regard to the magnetic field distributions of the saddle coil and the Lee-Whiting coil within a range of 80 mm along their axes, the results show that the maximum relative error between the analytical method and the finite element method results is 0.08% and 0.06%, respectively; the maximum relative error between the experimental values and the analytical values is 0.29% and 0.13%, respectively, thus confirming the validity of the analytical model. The results of this research have far-reaching implications for the research of quantum precision measurement devices and triaxial uniform field coils.

A Constant Current Wireless Power Transfer Scheme with Asymmetric Loosely Coupled Transformer for Electric Forklift

Due to the numerous advantages such as being convenient, safe, and contactless, wireless power transfer (WPT) is becoming the mainstream charging method for electric vehicles. This paper presents a constant current WPT system with asymmetric loosely coupled transformer for electric forklifts using lead-acid batteries. First, based on the Neumann formula, this paper analyzes the mutual inductance of the coaxial rectangular coil, and designs an asymmetric loosely coupled transformer based on the practical application requirements, which makes the secondary side light and miniaturized. Second, the WPT system is analyzed in terms of the requirements of constant current charging, and the dual-LCL compensation is proposed according to the output current and power requirements. The transfer characteristics and anti-interference capability of the topology are analyzed. The constant current output feature of the system under the condition of variable load is demonstrated. After that, a dual-active bridge secondary-side independent control strategy is proposed, the phase shift angle is adjusted to ensure constant charging current and high efficiency of the system. Finally, a wireless charging experimental platform is established in accordance with the proposed asymmetric loosely coupled transformer and WPT system. The system can achieve 45 A constant current output and 3 kW output power with 91.2% transmission efficiency.

Строгие и приближенные выражения для коэффициентов взаимной индукции и электродинамических сил соосных витков и плоских (дисковых) катушек с током

Object and purpose of research. The paper is concerned with the mutual inductance coefficients of co-axial circuits in a planar coil system. Known modifications for mutual inductance and electrodynamic forces in a system of co-axial circuits are written, and relations for their calculation are compared. Materials and methods. For this purpose the methods of mathematical physics and theoretic electric engineering are used. Main results. Alternative expressions are given for mutual inductance coefficients of co-axial coils and electrodynamic forces between the live coils. Curves of mutual inductance are plotted for planar coils with the distance between planes equal to 2 cm and the distance between coil turns Р equal to 1 сm and the distance between coil turns N equal to 0.5 сm, 0.4 сm & 0.3 сm. Conclusion. Relations have been derived for calculation of mutual inductance coefficients and electrodynamic forces at current passage in planar co-axial coils, which are very important for wireless transfer of power.

Electrical anisotropy of terrigenous deposits: a brief overview of approaches to its determination from electrical logging data in vertical wells

The article briefly reviews a number of publications on the problem of determining rocks electrical resistivity anisotropy (primarily of sedimentary genesis) using downhole resistivity logs. We provide the information on the main causes of sandy-clay sediments micro- and macroanisotropy according to Russian papers and the history of the model-based approaches to the resistivity anisotropy description according to Russian and foreign articles. We analyze the main approaches to the vertical resistivity estimation. Both new hardware solutions aimed at direct measurement of electromagnetic field components sensitive to anisotropy and methodological techniques for extracting this information from the signals of "conventional" resistivity logging tools are considered according to published studies. The hardware solutions are multicomponent measurements with inclined and perpendicular (to the tool axis) coils, as well as with coaxial toroidal coils. Methodological techniques include combining data measured by tools with different types of medium excitation, for example, induction and galvanic. A number of papers suggest a two-step scheme: the first step is to determine the horizontal resistivity using induction arrays data, and the second step is to determine the vertical resistivity using focused lateral logs. Such schemes are implemented using numerical inversion algorithms and in some cases by inventing transformations of measured signals. Adding anisotropy to the interpretational model is based on a priori data (core studies, microresistivity logs). In the absence of a priori data, anisotropy is added when it is impossible to reconcile the parameters of isotropic models built independently based on logs with different type of excitation. A special focus of the review is on the development of the theory of unfocused lateral logging (BKZ) method by Soviet and Russian scientists and on the history of research on the electrical anisotropy influence on the signals of gradient probes. Due to the widespread use of the method in the USSR, this topic is presented in a number of papers revealing the results of anisotropic geoelectric models theoretical studies, numerical and physical modeling of BKZ logs and methodological developments for their interpretation.

Electrical anisotropy of terrigenous deposits: a brief overview of approaches to its determination from electrical logging data in vertical wells

The article briefly reviews a number of publications on the problem of determining rocks electrical resistivity anisotropy (primarily of sedimentary genesis) using downhole resistivity logs. We provide the information on the main causes of sandy-clay sediments micro- and macroanisotropy according to Russian papers and the history of the model-based approaches to the resistivity anisotropy description according to Russian and foreign articles. We analyze the main approaches to the vertical resistivity estimation. Both new hardware solutions aimed at direct measurement of electromagnetic field components sensitive to anisotropy and methodological techniques for extracting this information from the signals of "conventional" resistivity logging tools are considered according to published studies. The hardware solutions are multicomponent measurements with inclined and perpendicular (to the tool axis) coils, as well as with coaxial toroidal coils. Methodological techniques include combining data measured by tools with different types of medium excitation, for example, induction and galvanic. A number of papers suggest a two-step scheme: the first step is to determine the horizontal resistivity using induction arrays data, and the second step is to determine the vertical resistivity using focused lateral logs. Such schemes are implemented using numerical inversion algorithms and in some cases by inventing transformations of measured signals. Adding anisotropy to the interpretational model is based on a priori data (core studies, microresistivity logs). In the absence of a priori data, anisotropy is added when it is impossible to reconcile the parameters of isotropic models built independently based on logs with different type of excitation. A special focus of the review is on the development of the theory of unfocused lateral logging (BKZ) method by Soviet and Russian scientists and on the history of research on the electrical anisotropy influence on the signals of gradient probes. Due to the widespread use of the method in the USSR, this topic is presented in a number of papers revealing the results of anisotropic geoelectric models theoretical studies, numerical and physical modeling of BKZ logs and methodological developments for their interpretation.

Thickness Measurement Based on Eddy Current Sensor With Coaxial Double Coil for Chemical Mechanical Polishing

Real-time and accurate thickness measurements of copper films on 300-mm silicon wafers are utilized to improve global planarization, control polishing pressure, and avoid dishing and erosion caused by under-polishing and over-polishing during chemical mechanical polishing (CMP) of metals. Nevertheless, the requirements of nanometer-scale measurement sensitivity, wide measurement range from tens of nanometers to 2 μm, and high edge measurement performance make eddy-current thickness measurement extremely challenging. Therefore, we proposed a concise and effective theoretical model to analyze the measurement range and sensitivity in both the amplitude- and phase-based methods. The advantages and disadvantages of the two methods are compared and discussed systematically through simulations and experiments. The effects of the lift-off distance and frequency of excitation signal on measurement sensitivity, range, and edge measurement performance are also examined. The results show that the proposed theory can be used to improve measurement range and sensitivity. And the double-sensor system demonstrated better edge measurement performance than a single coil. Finally, a double-coil eddy current thickness measurement system designed with an average sensitivity of 1.9 mV/nm, a measurement range of 60 nm to 2 μm, and an edge attenuation position of 141.5 mm at a lift-off distance of 3.5 mm can be utilized in the amplitude-based method for advanced Cu-CMP.

Mutual inductance of two coaxial rectangular PCB coils incorporating magnetic layer

Abstract The wireless connection distance between the transmission and reception coils of printed circuit boards (PCB) influences the mutual inductance and affects circuit performance. In this study, the mutual inductance M of PCB coils was investigated, and two analytical methods were presented for calculating the mutual inductance between two coaxial rectangular planar PCB coils incorporating magnetic layer. The results were acquired through calculations by using the Neumann integral and Biot-Savart methods. The complete integral calculations and detailed demonstrations of the two methods are presented. The obtained formulas were introduced in some examples of coils with different number of turns. The analytical and experimental results were compared, and a strong agreement between them was observed.

The full phase space dynamics of a magnetically levitated electromagnetic vibration harvester

We consider the motion of an electromagnetic vibrational energy harvester (EMVEH) as function of the initial position and velocity and show that this displays a classical chaotic dynamical behavior. The EMVEH considered consists of three coaxial cylindrical permanent magnets and two coaxial coils. The polarities of the three magnets are chosen in such a way that the central magnet floats, with its lateral motion being prevented by enclosion in a hollow plastic tube. The motion of the floating magnet, caused by e.g. environmental vibrations, induces a current in the coils allowing electrical energy to be harvested. We analyze the behavior of the system using a numerical model employing experimentally verified expressions of the force between the magnets and the damping force between the floating magnet and the coils. We map out the phase space of the motion of the system with and without gravity, and show that this displays a fractal-like behavior and that certain driving frequencies and initial conditions allow a large power to be harvested, and that more stable states than two exists. Finally, we show that at leasts fifth order polynomial approximation is necessary to approximate the magnet-magnet force and correctly predict the system behavior.

Accurate Computation of Mutual Inductance of Non Coaxial Pancake Coils

The computation of self and mutual inductances of coils is a classic problem of electrical engineering. The accurate modeling of coupled coils has received renewed interest with the spread of wireless power transfer systems. This problem has been quite well addressed for coplanar or perfectly coaxial coils but it is known that the misalignment conditions easily lead to a sharp decrease in the efficiency. Hence, it is crucial to take misalignment into account in order to properly design the overall wireless power transfer system. This work presents a study to compute analytically the mutual inductance of non-coaxial pancake coils with parallel axes. The accuracy of the proposed methodology is tested by comparison with the numerical results obtained using the tool Fast-Henry. Then, a wireless power transfer system, comprising a full bridge inverter is considered, showing the impact of the misalignment on the coupling between two pancake coils and, thus, between the source and the load.

Simulation of Magnetic Force between Two Coaxial Coils with Air Core and Uniform Flow in MATLAB

Magnetic field is one of the most used sciences in today's industry, which is applied in many cases such as electromagnets, electric motors, and generators, electric transformers, electromagnetic wave propagation in antennas, magnetic levitation, etc. that has led to many types of research in this field. Therefore, correct calculation of magnetic force is one of effective and important discussions in this field. One of the subsets of the force calculation is between two coils. The purpose of this research is to implement and simulate two cylindrical coaxial coils with uniform current. We calculate the axial magnetic force of the cylindrical coil by simulating and implementing two coils and applying numerical integration methods, parametric integration, and finite element method in MATLAB software. The results show that the implemented codes are able to calculate the force between two coils quickly, with small error, and with high accuracy. These results will help to implement a proper system with real term and very high accuracy by choosing the best method that fits your system's constraints, conditions, and type.

Определение взаимных индуктивностей и электро- динамических сил между катушкой и соосным соленоидом при симметричном расположении

Object and purpose of research. Mutual inductances are among the main parameters of electrical circuits, and their determination is the most important task for studying the physical processes occurring in them, including the occurrence of electrodynamic forces. Coaxial coils and solenoids are very common part of electrical devices, and finding mutual inductances and electrodynamic forces in them has a great practical importance. Materials and methods. Methods of theoretical electrical engineering are used. Main results. Expressions for mutual inductance are obtained, and they are based on the decomposition of the solenoid into its external and internal parts relative to the end planes of the coil. Conclusion. On the basis of the undertaken analysis, alternative expressions for mutual inductances are obtained.

Development of Methodological Bases of the Processes of Steam Formation in Coil Type Boilers Using Solar Concentrators

A mathematical model of the vaporization process in the coil is developed, taking into account the experimental data. To investigate and visualize the evaporation procedure in the coil, a mathematical pattern of the vapor-liquid mixture motion is compiled and reproduced. In the methodology of the study of the movement of the steam-water mixture, correction coefficients are proposed for calculating the velocities of the coolant in non-standard coaxial coils. The parameters were calculated using data sensitivity analysis and data validation was performed by repeated tests; uncertainty was detected when using the instruments, as well as the total extended uncertainty, the upper and lower limit of uncertainty for each measured parameter. In addition, as part of the steam generator set, solar collectors operate in the summer mode. Using the example of the studied steam generator operating in the conditions of an oil and gas field in the subarctic climate, it is shown that it is possible to use air-type solar collectors for the ventilation system of the production room, as well as water-heating solar collectors for technical systems of hot water supply and chemical water treatment.

Design of coaxial coils using hybrid machine learning.

A coil system to generate a uniform field is urgently needed in quantum experiments. However, general coil configurations based on the analytical method have not considered practical restrictions, such as the region for coil placement due to holes in the center of the magnetic shield, which could not be directly applied in most of the quantum experiments. In this paper, we develop a coil design method for quantum experiments using hybrid machine learning. The algorithm part consists of a machine learner based on an artificial neural network and a differential evolution (DE) learner. The cooperation of both learners demonstrates its higher efficiency than a single DE learner and robustness in the coil optimization problem compared with analytical proposals. With the help of a DE learner, in numerical simulation, a machine learner can successfully design coaxial coil systems that generate fields whose relative inhomogeneity in a 25 mm-long central region is ∼10-6 under constraints. In addition, for experiments, a coil system with 0.069% inhomogeneity of the field, designed by a machine learner, is constructed, which is mainly limited by machining the precision of the circuit board. Benefitting from machine learning's high-dimension optimization capabilities, our coil design method is convenient and has potential for various quantum experiments.

Design of Simulated Magnetic Gun

STM32F103 single-chip microcomputer is used as the control unit of the simulated electromagnetic squint. The single-chip microcomputer is used to control the function of launching shell and steering gear angle, and the steering gear is used to control the launching angle and direction of the electromagnetic squint. In the design of electromagnetic gun, coaxial coil gun is used as the main part, and two batteries are used as the energy supply device. Then the electromagnetic relay connected with the single-chip microcontroller controls the cycle charging. Firstly, 12V DC power is input into the circuit by the DC stabilized voltage power supply. After the current enters into the circuit, it is divided into two branches. One branch flows through the boosting circuit of electromagnetic relay to charge the thyristor capacitor. With the switch off, the instantaneous discharge of the capacitor generates an inverter magnetic field in the coil, which pushes the metal projectile out at a high speed. What the electromagnetic relay does is to boost the voltage. What the thyristor capacitor needs is high voltage current charging. Another branch supplies 5V DC power to the steering gear through the step-down electromagnetic relay to support the rotation of the steering gear. The system obtains the target position through openmv, and STM32 uses PWM wave to control the rotation angle and direction of the steering gear.