Coil Resistance Research Articles

Investigation on the Electrical Contact Resistance of Soldered Metal Insulation REBCO Coil

No-insulation (NI) winding techniques are widely used in fabricating thermally, mechanically, and electrically robust REBCO magnets. However, NI coils have disadvantages during charging operation, such as charging delay and heat loss due to leakage current. Leakage current can be reduced by increasing contact resistance. Metal-insulation (MI) winding methods are also used by co-winding high-resistive metal insulators between the winding turns of REBCO wires. Although the contact resistance of MI coils can be substantially increased, quantitative estimation of the magnet contact resistance is difficult owing to the dry-contact between the winding turns. Moreover, special care is needed during epoxy impregnation of MI or NI magnets owing to delamination problems induced by the epoxy layer between the winding turns. In this study, a soldered metal insulation (SMI) method is proposed to remove the drawbacks of the MI coil, such as the hardly predictable contact resistance and the delamination issue during conduction cooling applications. The SMI coils were wound using a tin-plated stainless-steel (SS) tape between the REBCO wires as in the MI coil and they were heated in a furnace to produce soldered contacts between winding turns. To investigate the electric characteristics, sudden discharge and charge/discharge experiments were conducted at 77 K. In this paper, the test coils were fabricated using the NI, MI, and SMI winding methods and the contact resistance of each coil was investigated. The results show that the SMI winding method can be used to create expected or controllable contact resistance.

Results of All ITER TF Full-Size Joint Sample Tests in Japan

Nine toroidal field (TF) coils have been developed in Japan for the international thermonuclear experimental reactor (ITER). The joint resistance of TF coil should satisfy the requirement of smaller than 3 nano-ohm at 2 T of external magnetic field and 68 kA of transport current. Full-size joint sample (FSJS) tests were performed for joint development and for TF coil manufacture, as part of the process control. 11 FSJS tests are conducted in total. FSJS tests were conducted with assistance from a test faculty in the National Institute for Fusion Science as reported in a previous paper. All FSJS tests successfully satisfied the requirement of resistance less than 3 nΩ at 2 T. Additionally, the TF coil joints are subjected to cyclic electromagnetic force and warm-up/cool-down during the ITER operation. The authors investigated the joint performance for the abovementioned influence. The results showed no degradation in the joint resistance. Thus, the TF joint developed in Japan was qualified successfully.

Eddy currents in multilayer coils

This article considers an example of eddy current behaviour that has not been described previously in textbooks and physics education journals. This phenomenon involves a sharp rise in the active resistance of a multilayer coil with increasing alternating current frequency. This effect is not explained by the classic skin effect and is not related to losses in a core. The results of measurements of the frequency dependence of the active resistance of multilayer coils obtained by the resonance method and the results of calculating this dependence in the framework of the tape model of a multilayer solenoid are presented. The special case of relatively low frequencies is analysed when the classic skin effect is weak in a solitary wire. However, the active resistance of a multilayer coil is significantly higher than its DC resistance. A schematic model of the observed effect is proposed. The analysed example of eddy currents is easy to realize in an experiment and open to clear physical interpretation. It might be appropriate for students of various specialities to discuss this effect in intermediate or advanced physics laboratories.

Dynamics of laser-generated magnetic fields using long laser pulses.

We report on the experimental investigation of magnetic field generation with a half-loop gold sheet coil driven by long-duration (10ns) and high-power (0.5 TW) laser pulses. The amplitude of the magnetic field was characterized experimentally using proton deflectometry. The field rises rapidly in the first 1ns of laser irradiation, and then increases slowly and continuously up to 10ns during further laser irradiation. The transient dynamics of current shape were investigated with a two-dimensional (2D) numerical simulation that included Ohmic heating of the coil and the resultant change of electrical resistivity determined by the coil material temperature. The numerical simulations show rapid heating at the coil edges by current initially localized at the edges. This current density then diffuses to the central part of the sheet coil in a way that depends both on normal current diffusion as well as temporal changes of the coil resistance induced by the Ohmic heating. The measured temporal evolution of the magnetic field is compared with a model that determines a solution to the coil current and voltage that is consistent with a plasma diode model of the drive region and a 2D simulation of current diffusion and dynamic resistance due to Ohmic heating in the laser coil.

Load Resistance Optimization of Bi-Stable Electromagnetic Energy Harvester Based on Harmonic Balance.

In this study, a semi-analytic approach to optimizing the external load resistance of a bi-stable electromagnetic energy harvester is presented based on the harmonic balance method. The harmonic balance analyses for the primary harmonic (period-1T) and two subharmonic (period-3T and 5T) interwell motions of the energy harvester are performed with the Fourier series solutions of the individual motions determined by spectral analyses. For each motion, an optimization problem for maximizing the output power of the energy harvester is formulated based on the harmonic balance solutions and then solved to estimate the optimal external load resistance. The results of a parametric study show that the optimal load resistance significantly depends on the inductive reactance and internal resistance of a solenoid coil––the higher the oscillation frequency of an interwell motion (or the larger the inductance of the coil) is, the larger the optimal load resistance. In particular, when the frequency of the ambient vibration source is relatively high, the non-linear dynamic characteristics of an interwell motion should be considered in the optimization process of the electromagnetic energy harvester. Compared with conventional resistance-matching techniques, the proposed semi-analytic approach could provide a more accurate estimation of the external load resistance.

Radio Frequency Coils for Hyperpolarized 13C Magnetic Resonance Experiments with a 3T MR Clinical Scanner: Experience from a Cardiovascular Lab

Hyperpolarized 13C magnetic resonance (MR) is a promising technique for the noninvasive assessment of the regional cardiac metabolism since it permits heart physiology studies in pig and mouse models. The main objective of the present study is to resume the work carried out at our electromagnetic laboratory in the field of radio frequency (RF) coil design, building, and testing. In this paper, first, we review the principles of RF coils, coil performance parameters, and estimation methods by using simulations, workbench, and MR imaging experiments. Then, we describe the simulation, design, and testing of different 13C coil configurations and acquisition settings for hyperpolarized studies on pig and mouse heart with a clinical 3T MRI scanner. The coil simulation is performed by developing a signal-to-noise ratio (SNR) model in terms of coil resistance, sample-induced resistance, and magnetic field pattern. Coil resistance was calculated from Ohm’s law and sample-induced resistances were estimated with a finite-difference time-domain (FDTD) algorithm. In contrast, the magnetic field per unit current was calculated by magnetostatic theory and a FDTD algorithm. The information could be of interest to graduate students and researchers working on the design and development of an MR coil to be used in 13C studies.

Research on remaining service life prediction of platform screen doors system based on genetic algorithm to optimise BP neural network

ABSTRACT The platform screen door system related to the safety of passengers, vehicle and station operation in rail transit is the research object. Relay, the key component of the PSD system, is selected as the breakthrough point, and the number of pull-in is used as the evaluation index of the service life of the relay. The precise and complex mapping between the influencing factors of the relay (coil resistance, pull-in voltage, release voltage, pull-in time, release time and contact resistance) and the remaining service life of the PSD system are established based on genetic algorithm to optimise BP neural network, and a new model for predicting the remaining life of the PSD is constructed. The PSD system of Guangzhou Metro Line 8 – KeCun Station is taken as the experimental test object. By comparing the BP algorithm, the PSO-BP algorithm and the GA-BP algorithm, it is demonstrated in detail how the prediction model can effectively predict the remaining service life of the PSD system with high precision, so that the equipment early warning before failure occurs to ensure the normal operation of subway lines. Experimental examples effectively prove the stability and accuracy of the GA-BP algorithm proposed.

Analysis of Magnetic Coupling Resonance Efficiency of Superconducting Radio Power String Familiar with Magnetic Resonance

This paper presents a superconducting wireless transmission system whose transmitting coil adopts superconducting material and receiving coil to adopt copper material which can solve the problem of transmission efficiency of wireless transmission system well. Firstly we analyze magnetic coupling resonant wireless transmission principle; then measure superconducting coil resistance and copper coil resistance calculate analyze system quality factor change with frequency. Finally experiment measurement of transmission efficiency of superconducting-copper magnetic coupling resonant wireless transmission system analyzes the relationship between transmission efficiency and axial offset and radial offset distance. Experimental results show that superconducting wireless transmission systems can improve transmission efficiency significantly compared with copper wireless transmission systems. Compared with copper wireless transmission systems, superconducting wireless transmission systems have at least 12.4% efficiency enhancement during axial offset, while at least 11.3% efficiency increases during radial migration. While short distance radial migration (1~4cm), superconducting wireless transmission systems have almost constant transmission efficiency. Provide some technical reference for Superconducting wireless transmission.

Simulation of seawater eddy current loss in in-situ detection system for the magnetic properties of seabed sediments

This paper mainly simulates and analyzes the working conditions of the in-situ detection system for the magnetic properties of seabed sediments in the marine environment. Firstly, the causes and influencing factors of eddy current loss in seawater are analyzed. Secondly, the influence of seawater eddy current loss is equivalent to seawater impedance circuit, and the influence on coil resistance, inductance and magnetic field generated by the coil is qualitatively analyzed. Finally, a COMSOL simulation model is built to verify the mentioned-above theoretical analysis. The simulation results show that compared with those in the air environment, the equivalent resistance of the coil increases, the equivalent inductance decreases and the magnetic field generated by the coil decreases in the marine environment.

Magnetic Field Energy Harvesting From Current-Carrying Structures: Electromagnetic-Circuit Coupled Model, Validation and Application

Magnetic field energy harvesters (MFEHs) from current-carrying structures/conductors are usually modelled as decoupled electromagnetic and electrical systems. The current-carrying structures may affect the performance of MFEH through the generation of the eddy current and the alteration of the magnetic reluctance. Moreover, the load circuit affects the current generated in the coil and therefore the flux density and eddy current generated. The effects of the current-carrying structure and the load circuit cannot be fully described by the decoupled models. This work develops a finite element model (FEM) that fully couples the electromagnetic and electrical systems by simulating both the magnetic field and eddy current distribution of an MFEH connected to an electrical circuit. The FEM first simulates the coil inductance and resistance of a magnetic field energy harvester (MFEH) placed close to a current-carrying structure exemplified by a rail track. The FEM then simulates the outputs of the MFEH connected to an electrical circuit consisting of a compensating capacitor and optimal load resistor determined by the first step. An MFEH was fabricated and tested under a section of current-carrying rail track. Both experiment and simulation show an increase of both coil resistance and inductance when the MFEH is placed close to the rail track. The good agreement between experimental and simulation results validates that the FEM can predict the full-matrix performances of the MFEH, including the coil parameters, power output and magnetic flux density under the influence of the current-carrying structure and the load circuit. Simulation results reveal that in addition to the permeability of the magnetic core, the electrical conductivity and magnetic permeability of the current-carrying structure considerably affect the performance of the MFEH, which cannot be predicted by decoupled models.

Short-circuit Current Reduction in Auxiliary Network of Traction Substations

The article analyzes short circuit current reduction due to three main factors: electrical arc, cable heating and contact and coil resistance in auxiliary network of traction substations. The research was made using ETAP software module Unbalance Short Circuit, where mathematical model of dynamic arc, as it is described by Russian and abroad scientists, iterative cable heating as it is described in Russian and European standards and contact resistance were implemented. Mathematical model includes power grid, auxiliary transformer, circuit breakers, current transformer, and cable. Cable size varies to show influence of each above-mentioned factors. Calculations were made using phase domain method and all the parts of auxiliary network were considered. The results show up to 60 percent decrease in three-phase short circuit current considering three factors together. It influences the ability to trip short circuit current by backup protections, fault-clearing time, cable sizing and the power supply quality. Neglect of one or more factors may, in some cases, mean insensitivity of the protection and the inability to trip the short circuit current in time.

Research basic parameters and justification of choice of gas injectors for alternative biogas fuel

In connection with the trend of shortage of commercial fuels for engines in Ukraine and the world, the production of alternative fuels is developing, including biogas. The use of biogas fuel on a modern internal combustion engine equipped with gas equipment of 4-5 generations can create a number of difficulties. This is due to the low heat of combustion of untreated biogas, the presence of moisture and the specifics of the operation of the nozzles. And, therefore, for the correct choice of nozzles, it is necessary to conduct a study and analysis of a number of basic indicators of their operation and, based on the data obtained, recommend their optimal parameters. In gas nozzles, as in gasoline ones, there are a number of important parameters on which stability and uniformity of engine operation, fuel consumption, reliability, etc. depend. These include: linear operation; nozzle reaction time; coil resistance; response time; ability to maintain factory performance; resource of work. For research, we selected nozzles of 4 generations of common manufacturers, namely: Matrix; Barracuda; Valtek; Hana; Keihin. In terms of linea-rity, Valtek nozzles have low performance, and therefore use on engines can lead to increased biogas consumption, reduced engine performance and valve burnout. Keihin nozzles have high rates in this aspect of research, and therefore they will provide maximum efficiency of biogas combustion on the engine. High reaction time in Keihin nozzles. Barracuda nozzles are very close to working with Keihin, which means that their use will not impair engine performance. The factory characteristics of the nozzles, namely the coil resistance is the optimal Keihin nozzle, and the lowest values ​​in Valtek nozzles, the response (response) time of the Matrix, Hana and Keihin nozzles is quite close to 2 ms, which will provide quick response and wear, and the Barracuda and Valtek nozzles Keihin, Matrix and Barracuda nozzles provide the ability to maintain factory characteristics in the range from 2 to 5%, and the worst performance in Valtek is up to 20%, the service life of the nozzles, subject to timely servicing, is the largest Keihin nozzle, Matrix and Hana, which is from 200 to 250 thousand km, and the lowest indicator in Valtek and Matrix injectors is a resource from 70 to 100 thousand km. So, according to the results of the research, Keihin nozzles are recommended for use on engines in the process of their conversion to gas fuel. Their application will provide maximum efficiency and economy of the engine.

Eksperimentalno istraživanje uticaja paralelnih električnih opterećenja na performanse elektromagnetnog sakupljača energije baziranog na vibracijama

At present, the researchers are grappling with the problems of maximizing the output power from a vibration-based electromagnetic energy harvester (VBEH). The parameters affecting the VBEH output power are: electrical damping ratio (ze), mechanical damping ratio (zm) and load impedances of shunted electrical load. Therefore, in this work, the experimental studies are carried out to study the effect of shunted electrical load on: i) the power output of VBEH and, ii) the determination of ze which maximizes the output power. For this purpose, a VBEH is designed and developed to obtain high open-circuit voltage. The effect of resistive, inductive, and capacitive loads on output power of VBEH is investigated using experimental setup developed exclusively for the same. The experimental results reveal that the output power of VBEH is maximum: i) at the resonant frequency ii) when equivalent resistive load impedance equals the internal resistance of electromagnetic coil and iii) value of ze is very small when compared to zm.

High Efficiency PMSM With High Slot Fill Factor Coil for Heavy-Duty EV Traction Considering AC Resistance

Electric vehicle (EV) systems require a high energy-efficiency traction motor so that the motors for EV traction should achieve high efficiency and power density. Hence, a permanent magnet synchronous motor (PMSM) for EV traction using a maximum slot occupation (MSO) coil has been investigated in this study. By applying the MSO coil, high torque density was achieved, but an additional loss, which decreases the efficiency, was incurred through alternating current (AC) resistance. To reduce the AC resistance of the MSO coil, the following process was performed: First, by investigation using the analytical method, pole/slot numbers, current density and number of parallel circuits affecting the frequency, the shape and number of conductors were chosen as important variables. Resistances of the MSO coil with a stator core were analyzed according to the chosen variables above. From the results, MSO coil applied PMSM with proper pole/slot numbers, current density, and parallel circuits was determined to improve the efficiencies at the base and maximum speeds. To accurately estimate the efficiency of the determined model, loss evaluation methods were explained. Subsequently, the determined MSO coil applied model was compared with the conventional model having round wires, and the improvements were verified by load testing.

Research on neutral point grounding mode and single-phase earth fault location of medium voltage island microgrid

For medium voltage islanding microgrid, the voltage clamp of the main network neutral arc suppression coil or small resistance is lost. Multiple PTs parallel operation will occur because different entities of a microgrid independently measure the voltage. It is necessary to consider the influence of multi PTs ferroresonance on the neutral grounding mode of islanding microgrid. The neutral point ungrounded, neutral point grounded by arc suppression coil and neutral point grounded by small resistance are analyzed respectively, considering multi PTs ferroresonance and single-phase earth fault location, it is determined that the islanded microgrid adopts neutral point grounded by small resistance. On this basis, the zero sequence current distribution is used to locate the single-phase earth fault. Finally, a simulation example is built to verify the correctness of the proposed method.

Method for Quantifying Variation in the Resistance of Electronic Cigarette Coils.

In electronic nicotine delivery systems (ENDS), coil resistance is an important factor in the generation of heat energy used to change e-liquid into vapor. An accurate and unbiased method for testing coil resistance is vital for understanding its effect on emissions and reporting results that are comparable across different types and brands of ENDS and measured in different laboratories. This study proposes a robust, accurate and unbiased method for measuring coil resistance. An apparatus is used which mimics the geometric configuration and assembly of ENDS reservoirs, coils and power control units. The method is demonstrated on two commonly used ENDS devices—the ALTO by Vuse and JUUL. Analysis shows that the proposed method is stable and reliable. The two-wire configuration introduced a positive measurement bias of 0.086 (Ω), which is a significant error for sub-ohm coil designs. The four-wire configuration is far less prone to bias error and is recommended for universal adoption. We observed a significant difference in the coil resistance of 0.593 (Ω) (p < 0.001) between the two products tested. The mean resistance and standard deviation of the reservoir/coil assemblies was shown to be 1.031 (0.067) (Ω) for ALTO and 1.624 (0.033) (Ω) for JUUL. The variation in coil resistance between products and within products can have significant impacts on aerosol emissions.

Effects of electronic cigarette heating coil resistance and liquid nicotine concentration on user nicotine delivery, heart rate, subjective effects, puff topography, and liquid consumption.

Electronic cigarette (ECIG) nicotine delivery and other effects can be influenced by device and/or liquid characteristics and user puffing behavior. One class of ECIGs includes "sub-ohm" devices that incorporate heating coils with resistance less than 1 ohm (Ω), lower than that observed in conventional devices (e.g., ≥1.5 Ω). Relative to conventional ECIGs that operate at ≤10 W, low-resistance coils can be used to increase device power (e.g., 40-300 W). However, little is known about the individual and combined effects of ECIG power, manipulated by coil resistance, and liquid nicotine concentration on ECIG acute effects. Experienced ECIG users (N = 32) completed 4 sessions that differed by ECIG power and coil resistance (40.5 W, 0.5 Ω or 13.5 W, 1.5 Ω) and liquid nicotine concentration (3 or 8 mg/ml). In each session, participants used a 4.5-V Kanger SUBOX ECIG in a 10-puff directed and 60-min ad libitum bout. Nicotine delivery, heart rate, subjective effects, puff topography, and liquid consumption were measured. Nicotine delivery was greatest in the 8mg/ml+0.5Ω condition and lowest in the 3mg/ml+1.5Ω condition. The greatest reduction in abstinence symptoms were observed in the 8mg/ml+0.5Ω condition, although the highest ratings for satisfaction and liking were reported in the 3mg/ml+0.5Ω condition. Use of ECIGs containing 3 mg/ml nicotine liquid resulted in longer and larger puffs and increased puff frequency, though high-power/low-resistance ECIGs resulted in greater consumption of ECIG liquid. ECIG device and liquid characteristics and user puff topography should be considered simultaneously when making regulatory decisions aimed at protecting public health. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Paramagnetic resonance in La2NiMnO6 probed by impedance and lock-in detection techniques

We studied the frequency-dependent (f = 1 GHz to 5 GHz) microwave absorption in the double perovskite La2NiMnO6 at room temperature using two cavity-less methods: An indirect impedance method that uses a radio frequency impedance analyzer and a folded copper strip coil for the frequency range f = 1–2.2 GHz and a lock-in based broadband setup using a coplanar waveguide for microwave excitation in the frequency range f = 2–5 GHz. The high-frequency resistance of the strip coil exhibits a sharp peak and the reactance curve crosses zero at a critical value of dc magnetic field as a consequence of the paramagnetic resonance in the sample. The resonance fields (Hr) obtained from both the techniques increase linearly with frequency. Line shape analysis and analytical fitting were performed to characterize the material in terms of its initial susceptibility and damping parameters. From the fit, we obtain a large spectroscopic g-factor, equal to 2.1284, which supports the presence of Ni2+ cation with strong spin-orbit coupling.

Research on motion characteristics and stability of 500kV fast mechanical switch

The key component of fast mechanical switch (FMS) is electromagnetic repulsion mechanism (ERM), and the stability of ERM has an important influence on fault breaking time and breaking performance of hybrid DC circuit breaker (DCCB). In this paper, a FMS based on ERM is designed. In order to improve the stability of the FMS, the key factors affecting the stability of the excitation coil resistance, the inductance of the excitation coil, the capacitance of the energy storage capacitor, the charging voltage and the ambient temperature are analyzed. Then, 2D ERM simulation model is set up and study the above parameters deviation and the change of environmental temperature on the repulsive force driving characteristics. In order to ensure that the ERM moves to 10mm in 2ms, and the time dispersion is less than ±0.2ms. The reasonable variation ranges of each parameter required for the stable action of the ERM and the appropriate working environment temperature are determined. Finally, the developed FMS prototype was tested for opening, temperature rise and consistency, and the test results were consistent with the simulation results.

Discoveries in Aerosol Science: Characterization of Nanoparticles Emitted From Metallic Coils in Electronic Cigarettes

Electronic (e-) cigarettes, also known as electronic nicotine delivery systems, are battery-operated devices that are growing in popularity worldwide. Although e-cigarettes are known to be safer than traditional cigarettes, their potential health risks have not been extensively reviewed yet. In this study, aerosol nanoparticles generated from e-cigarette heaters were characterized. Kanthal A1 (iron + chromium + aluminum) coils, without nicotine solution or a wick, were installed in an e-cigarette atomizer. The operating conditions were varied coil resistances (0.1–1.0 Ω), a set applied power (10 W), and a stable duty cycle (50%: 5 s on, 5 s off ). The size distribution and morphology of particles were collected by a scanning mobility particle sizer and evaluated by transmission electron microscopy, respectively. From an applied power of 10 W and a 50% duty cycle, the size and total number concentration (TNC) of particles emitted increased with greater coil resistances. Within these operating conditions, the average TNC of particles generated exhibited a steep decrease during the first 15 minutes of each trial. The TNC of particles decreased over time because surface oxidation (iron oxide layer) prevented further nanoparticle emission. As a result, a used coil may reduce the risk of the metal exposure from e-cigarettes. The results indicate that our designed and tested e-cigarette generation system is useful for future research that aims to investigate the health impacts of metallic particle inhalation on e-cigarette users.