Coil Resistance Research Articles

Research on the Characteristics of Wireless Power Transfer in Non-ferromagnetic Metal Pipe

With the development of various electronics, the way of transmitting energy by wire has brought increasingly negative effects on the operability and convenience of products. As wireless power transfer (WPT) technology requires no transmission lines, it has received increasingly wide attention. Most of the previous research on the technology of magnetic resonant coupling WPT mainly focused on the transmission of energy in the air. This paper establishes the wireless power transfer system model under non-ferromagnetic metallic environment and studies the effect of non-ferromagnetic metallic environment on coil self-inductance L, mutual inductance M and coil resistance R of WPT system. On this basis, the study on the relationship between coil diameter and mutual inductance is carried out for aluminium pipe, and the relationship between coil diameter and diameter of metal pipe at the maximum mutual inductance is fitted. Besides, experimental verification is conducted for the change of mutual inductance between the coils of WPT system in the aluminium pipe, presenting that the actual measurement results of mutual inductance in the aluminium pipe are consistent with the theory.

Low-frequency magnetic field shielding effect of artificial joint-free REBCO coils

The screening current induced in superconductors can passively shield external magnetic fields and hence provide a noise free environment for precision sensors and instruments. This paper presents a novel design employing artificial joint-free REBCO (REBa2Cu3O7-x, RE: rare earths) coils which can economically extend the field shielding space for larger instruments, e.g. clinical equipment. We compared the shielding factors of single, double and multi-coils, and confirmed a coil with Helmholtz construction as the optimal architecture. Due to the zero resistance of the joint-free REBCO coils, the shielding effectiveness reaches 80 dB at the center of coils, shielding 99.99% of the external magnetic field of 10 μT at 1 × 10−5 Hz, and 40 dB (99%) in a greater spherical space of 40 mm in diameter. Additionally, the shielding effectiveness does not decrease in the external magnetic field of 1 nT. Such a low frequency magnetic shielding effect implies promising applications for the present work, such as preventing interference magnetic fields from precision instruments, which generally require field sensitivity as low as the fT · Hz−1/2 range.

Coil and core design for inductive energy receivers

The design of coil/core transducers is important for maximizing the power density of inductive energy receivers for both inductive energy harvesting and power transfer. In this work, we present a study of core and coil performance, based on a simulated flux distribution corresponding to aircraft applications. The use of funnel-shaped soft magnetic cores boosts magnetic flux density by flux concentration and allows the use of a smaller diameter coil. This reduces the transducer mass as well as the coil resistance (RCOIL), thereby increasing the available power density. Analysis and simulation shows a fifty-fold power density increase from moderate funneling and another two-fold increase by coil size optimization. Results are compared with experimental measurements which demonstrate a 31 μW/g power density from alternating environmental magnetic fields in the 10 μT/360 Hz range.

Research on the Characteristics of Wireless Power Transfer in Ferromagnetic Metal Pipe

With the development of society, radio energy transmission technology has been paid more and more attention. However, in the actual application environment, the surrounding metal environment has a significant impact on the radio energy transmission performance. Based on the technology of MRR radio energy transmission, this paper establishes a two coil radio energy transmission model, and analyzes the influence of metal environment on the coil self inductance L, mutual inductance m and coil resistance R of the radio energy transmission system by finite element simulation. On this basis, aiming at the ferromagnetic metal environment, the steel pipe is selected as the research object to study the relationship between coil diameter and mutual inductance in the metal pipe, and the relationship between coil diameter and metal pipe diameter when the maximum mutual inductance is obtained through fitting analysis. At the same time, through the experiment, the mutual inductance between the coils of the wireless energy system in the steel tube is verified, and the experimental results are very consistent with the theory.

The Influence of Substrate Size Changes on the Coil Resistance of the Wireless Power Transfer System

Wireless power transfer (WPT) technology has been widely used in many fields. Nevertheless, in the field of high power transmission, such as the WPT system of electric vehicles, the power transmission efficiency of WPT system lags behind that of wired charging due to losses brought by substrate shielding materials. In this regard, the conduction resistance of Litz-wire coils without substrate is analyzed first in this paper. Secondly, the induction resistance of the coil with single-layer and double-layer substrate materials is modeled. Then, through the establishment of a coil simulation and experimental platform with a single-layer substrate, a contrastive analysis of the variation trend of coil equivalent series resistance (coil ESR) at changing thickness and area and constant volume of the substrate is carried out in combination with the theory. The variation law of coil ESR at changing thickness and area and constant volume of double-layer substrate is also explored at the end of this paper. This is expected to contribute to the reduction of coil losses in the WPT system through a systematic study of the influence of substrate size changes on the coil resistance of the WPT system.

Investigation and analysis of turn-to-turn contact resistance of a no-insulation YBCO pancake coil under time-varying

This paper is focused on the turn-to-turn contact resistance as a major source of the characteristic resistance of no-insulation YBCO pancake coil. Usually, the characteristic resistance of the coil is calculated by measuring decay time constant. However, we identify that the turn-to-turn contact resistance is not a constant value and changes with time. In order to verify this, one single pancake NI HTS coil consisting of 27 turns were fabricated with winding tension carefully maintained at a constant level. Through charge, discharge and sudden tests under time-varying, we obtain curves of the axial field at the centre, coil end-to-end voltage and an output current of power supply. In this paper, results show that the turn-to-turn contact resistance of NI coil varies with the time.

High Sensitive Detection of Volatile Organic Compounds Using Tin Oxide Semiconductor Sensors with Hot-Wire-Type Structures

Introduction Detection of VOCs (volatile organic compounds) has been required because it is detrimental to human health. In particular, in working environment with organic solvents, the need for VOC detectors has grown to reduce the damage to workers. For this purpose, we have developed SnO2 semiconductor sensors with hot-wire-type structures.The hot-wire-type semiconductor sensor can detect ppm concentration gas with a simple structure suitable for mass-production, resulting in practical use in various applications [1]. In this work, we have achieved high sensitivity and selectivity for VOCs by optimizing SnO2 loaded with several metal oxides. Moreover, the newly developed VOC sensor has excellent durability against the poisonous siloxane, leading to commercial products thanks to these advantageous characteristics.To improve convenience for portable use of VOC detectors, we have developed VOC sensors fabricated by micro electro mechanical systems (MEMS) technology to save power consumption [2]. The power consumption of the MEMS VOC sensor was greatly reduced in comparison with conventional hot-wire-type sensors, without sacrificing high sensitivity to VOCs. The low power consumption of the MEMS sensor makes it possible to extend the battery life, which would lead to further spread use of the VOC detectors. Experimental Figure 1 shows the structure of a hot wire semiconductor sensor, which consists of a platinum wire coil and a sintered SnO2 bead. A solution containing several metals was dropped and immersed in the sintered SnO2. Thereafter, metal oxides were supported on SnO2 by current heating to fabricate a hot-wire semiconductor VOC sensor. The coil served as both a heater and electrodes for the semiconductor bead; the total resistance of the sensor (Rs) was approximated by a parallel electric circuit consisting of the coil resistance and the semiconductor one (Fig.2). For the evaluation of the characteristics, the sensor output voltage (V s) was obtained by incorporating the sensor into a bridge circuit and applying a voltage. The operating temperature of the VOC sensor was controlled to be approximately 450 ℃. The sample gas sensitivity was calculated as difference between V s in mixture of air and sample gas (V s gas) and V s in clean air (V s air).Figure 3 shows a cross-sectional schematic of the MEMS VOC sensor. In the MEMS sensor, a Pt micro-heater/electrodes, patterned by using photolithography, was constructed on about 100 μm square insulating membrane cross-linked to the Si substrate. A sensitive layer of SnO2 with thickness of a few tens µm was deposited on the Pt micro-heater by thick film technology. After sintering the SnO2 thick film on the platinum pattern, several metal oxides were added. Results and Conclusions Figure 4 shows the typical gas sensitivity characteristics of the fabricated hot-wire-type semiconductor sensor to various VOCs. The sensor showed high sensitivity for vapors such as acetone, ethyl acetate, and toluene in a concentration range that affects human health. On the other hand, the sensor showed low sensitivity to interfering gases such as methane and hydrogen. These results demonstrate that the sensors have sufficient selectivity for practical use. Optimization of loaded metal oxides successfully controlled oxidation activity of SnO2 optimally, resulting in improved VOC sensitivity and further reduced interfering gas sensitivity. Furthermore, the sensor showed significantly better durability against toxic siloxane gas than the conventional one, resulting in long-life use in real field. The improved durability against siloxane poisoning is attributable to the controlled oxidation activity of SnO2 by loaded metal oxides. The developed sensor is useful for monitoring VOC as a practical detector that can measure in real time.Next, we investigated the MEMS VOC sensors. Quick thermal response owing to the miniaturized structure enabled us to achieve working temperatures (~500 °C) of the sensor only in 30 milliseconds. Thus, we could operate the MEMS sensor in a pulsed voltage mode, in which averaged power consumption was less than 1 mW. We confirmed that the MEMS sensors, even with the pulsed voltage operation, reproduced high sensitivity to VOCs obtained in the conventional sensor. In addition, the MEMS sensor exhibited long term stability for more than two years. The MEMS VOC sensor would contribute to the improvement of working environment with the spread use of VOC detectors.In conclusion, we have successfully developed hot-wire-type semiconductor VOC sensors ready for commercial use. We have also developed VOC sensors fabricated by MEMS technology to save power consumption.

Analysis and Experiment on Performance Improvement of IPPS at Low Temperature

The performance of inductive pulsed power supplies (IPPSs) is limited by excessive joule heat loss and low energy transfer efficiency. A significant reduction in the coil resistance can fundamentally ameliorate this problem. This article takes the meat grinder with self-charge capacitor and thyristor (SECT) circuit as an example to study the performance improvement caused by the reduction of the coil resistance. The influence of coil resistance on several performance indexes is analyzed by circuit analysis and simulation. Then, the experiment with an energy level of 40 kJ is carried out, in which the inductors have very low resistance due to immersion in liquid nitrogen. With low temperature, the charging energy and the output current peak value are increased by 37% and 19%, respectively, the pulsewidth of output current is increased by 257%, and the energy transfer capacitor is successfully self-charged compared to the performance of the same SECT circuit with room temperature. Thus, the feasibility of applying nitrogen cooling to IPPS is validated.

Vehicle vibration suppression using an inerter-based mechatronic device

As a two-terminal mechanical element, the inerter has been successfully deployed in various mechanical systems, such as automotives, multi-story buildings, and motorcycles. The introduction of the inerter allows the use of network synthesis to design a passive mechanical network, and can potentially facilitate the identification of practical and high performance mechatronic vibration absorbers. This paper provides an approach for optimal design of both the mechanical and the electrical parts for an inerter-based mechatronic device in vehicle suspension. The system considered includes a mechanical ball-screw inerter alongside an electric motor that is not driven but instead used passively with an electrical load applied across the terminals. The trade-offs in designing the ball-screw inerter and the permanent magnet electric machinery is discussed in detail. Two factors, namely, the coil resistance and the inductor resistance, are taken into account in the performance evaluation. Results show that the improvements in the road holding performance can reach 9.24% for the ideal suspension system with no diverse effect on the ride comfort and suspension travel performance, while a 5.77% improvement can be obtained when the effects of the coil resistance and the inductor are included.

Early Detection of Coil Failure in Solenoid Valves

This article describes the development and application of a model-based scheme for detecting the early signs of coil failure in solenoid valves. Contrary to other works, the proposed method simply isolates the fault-induced change in the coil resistance from thermal effects and provides a cost-effective solution with no comprehensive equipment demand. The model-based detection method employs a simple thermal model of the solenoid and an extended Kalman filter (EKF) for generating coil current residuals. The EKF utilizes measurements of coil voltage, coil current, ambient, and fluid temperature. The CUmulative SUM of the current residual is found to be sensitive to the early signs of coil failure. An experimental setup is utilized for evaluating the robustness of the detection method in the event of changing ambient temperature, convection, and fluid flow conditions. Results show that the method is able to detect the early signs of coil failure, and robust behavior and high detection probabilities are achieved for realistic fault sizes. The realistic fault sizes and the number of fault instances before failure are determined through extensive accelerated tests, where solenoids are operated at high temperature until failure.

Analysis of the power transfer and electrical performances of an embroidered textile loop antenna for near field communication (NFC) application

We present a new class of wearable textile antenna and analyse their performances through an electrical study. The developed prototypes have been realized by an embroidery process and are made of conductive twisted copper/polyester yarns on a cotton substrate. These antennas aim to transfer power and data thanks to the NFC technology, so the operating frequency is 13.56MHz and the maximal reading distance is around 10cm. The strong resistance of the yarn (4.20Ω/m) make us overlap three yarns to reach satisfactory electrical characteristics. Antennas are composed of a textile plan circular coil to which we add a usual capacitor. The study of coils electrical characteristics highlights a linear evolution of coil resistance and inductance in function of embroidery geometrical parameters. Also, these data show the feasibility of such antennas, especially through quality factor values reaching 45.

Measurement uncertainty evaluation by kurtosis method at calibration of electrical resistance standards using a comparator

The article provides examples of the application of electrical resistance standards in metrological practice. Existing methods for their calibration are analyzed. It is established that calibration using a comparator is the most accurate and common method for calibrating electrical resistance standards.A model for transferring the size of the resistance unit in calibration of electrical resistance standards using a comparator is considered. An expression is given for the evaluation of the value of measurand. The procedure for estimating the expanded measurement uncertainty based on the kurtosis method is described, and the uncertainty budget is drawn up. An example of evaluation of the measurement uncertainty in calibration of the resistance coil P321 using a resistance comparator P3015 is given. The coincidence of the obtained results with those got using the Monte Carlo method is shown.

Research on loop closing operation of hybrid grounding system based on distribution automation

During the loop closing operation, excessive loop current may occur because of the amplitude and phase difference of the busbar voltage on both sides of the loop point, causing overcurrent protection or quick-break protection maloperation. This paper takes the loop closing operation of 10 kV hybrid grounding model of arc suppression coil and low resistance in Hangzhou as an example, use ATP-EMTP software to build the simulation model. The factors affecting the size of the loop current are tested, and the specific conditions for the loop closing operation are determined. The conclusions have great significances for promoting the automatic loop closing operation of 10kV distribution network. The conclusions have great significances for promoting the automatic loop closing operation of 10kV hybrid grounding distribution network.

Automotive MR Shock Absorber Behaviour Considering Temperature Changes: Experimental Testing and Analysis

Abstract This study investigates the automotive magnetorheological (MR) shock absorber behaviour in conditions of changing temperature. Its temperature-dependent behaviour was quantified between ambient and maximal operating temperatures of the device. Aspects addressed include the temperature dependence of the control coil resistance in the absorber, the influence of operating current level on control coil temperature and the temperature dependence of the absorber force response and energy dissipation in the system. The results of experiments enabled us to evaluate the mechanical performance of the absorber at varied temperatures.

Low powered variable voltage E-Cigarette batteries under perform at higher power settings

Objective: Electronic Cigarettes (EC) use continues to increase with many efforts underway to develop dose-response relationships for clinical and sub-clinical purposes. This study investigated the battery performance of several variable voltage (VV) ECs capable of varied voltage outputs.Materials and Methods: Six brands of VV EC batteries were tested for dial setting accuracy (voltage) and power supplied during simulated vaping. All measurements were conducted using a single atomizer with two different resistance coils at four voltage settings in a blocked randomized structure. Battery dial settings were accurate when disconnected from an atomizer.Results: When powering an atomizer during simulated vaping, all batteries supplied power linearly up to approximately 8.5 watts. Beyond 8.5 watts all batteries began to undersupply power, plateauing around 9-10 watts, depending on the specific battery.Discussion: This behavior was not consistent with battery internal resistance. Undersupply of power at higher device settings will result in lower-than-expected nicotine (or THC) delivery and potentially lower pyrolysis products such as aldehydes.Conclusion: Studies seeking to associate VV EC power with psychological, physiological or toxicological effects should measure the actual power supplied or else a negative bias is likely to be observed in trials above 8.5 watts.

Understanding quench in no-insulation (NI) REBCO magnets through experiments and simulations

Present research on no-insulation (NI) rare earth barium copper oxide (REBCO) magnets have demonstrated their ability to produce high fields due to their compact nature. NI magnets have often been demonstrated to be self-protecting. However, evidence of mechanical damage in recent high field magnets, suggests that there are some issues about quench that must be resolved for this otherwise promising technology. This article attempts to explain multi-physics phenomena occurring during the quench of an NI magnet that can be used to elucidate quench behavior through experiments and simulations. A lumped circuit model is used for the circuit analysis where each coil is modeled as a single inductor with variable quench resistance in series and characteristic contact resistance in parallel. Three case studies have been analyzed: (1) a 3 double pancake (DP) standalone magnet, (2) a 2 DP coil in 31 T background, and (3) a high temperature superconductor/low temperature superconductor (HTS/LTS) hybrid user magnet that consists of a 13 T HTS insert and a 6 T LTS background magnet. Lessons learned from these analyses include: (1) characteristic resistance of NI coil rises during quench with the temperature rise; (2) influence of Hall effect exists on the voltage rise during quench; (3) over-current during quench can over-stress the coil; and (4) quench propagation from one end of the magnet generates significant unbalanced forces. This approach is expected to be used in the preliminary design of an ultra high field (>40 T) user magnet currently under design at the National High Magnetic Field Laboratory.

Frequency Properties of an Air-Cored Coil and Application to Conductivity Measurement

This study investigated the frequency properties of an air-cored coil and applied it to inspect conductivity change. Theoretical analysis and experimental study showed that what we measured is not the coil's own resistance and inductance but the equivalent ones which change with frequency. Case studies on conductivity measurement using a coil probe showed that we can greatly enhance measurement sensitivity by making the best of the coil's frequency properties. By utilizing the coil at frequencies that the coil's resistance and inductance are `frequency-invariant', we were able to detect conductivity change with high sensitivity on the basis of `same product of conductivity and frequency, ωσ(product of angular frequency and conductivity), same impedance' principle. The study also showed that we can use the coil's resonant properties, e.g., resonant frequency, resistance at resonant, to sense conductivity change, regardless of change on thickness. A slight variation of conductivity could be perceived by fine frequency adjustment. The results strongly suggest using a coil in accordance with its frequency characteristics.

Design Optimization of Inductive Power Transfer Systems Considering Bifurcation and Equivalent AC Resistance for Spiral Coils

This paper presents a design optimization algorithm for series-series compensated Inductive Power Transfer (IPT) system based on flat spiral coils, considering bifurcation phenomenon and AC equivalent resistance of the coils. Moreover, it finds the best values in the areas where the IPT system operates in Zero Voltage Switching (ZVS) condition. Equivalent AC resistance of spiral coils is modeled based on eddy currents simulations using Finite Element Method (FEM) and Maxwell simulator. Based on the FEM simulations, a new approximation method using separation of variables is proposed as a function of spiral coil’s main parameters. This paper shows that this model accurately derive equivalent resistance of the coils for a specific strand diameter, with almost 95% accuracy. Based on the proposed algorithm, several IPT systems are optimized in MATLAB software using Genetic Algorithm (GA). Finally, the proposed method has been verified using a laboratory prototype with output power of about 200 watts and operating frequency of about 85 kHz.

Reduction of AC Resistance of Litz Wire Coil for Wireless Power Transmission Using Magnetic Tape

High power wireless power transmission coils to be used for an electric vehicle (EV) and the automatic guided vehicle used in the plant (AGV) generally have the litz wire coil is used. The litz wire can reduce the high-frequency loss of the wireless power transmission coil. The smaller the number of strands, the easier it is to manufacture litz wires, but the higher the AC resistance. In addition, coil heat generation reduction and efficiency improvement are required. Therefore, the authors proposed a magnetic tape litz wire coil that reduces AC resistance and improves efficiency by winding magnetic tape around litz wire. The AC resistance was reduced from 73.9 to 64.9 mΩ by winding magnetic tape around the litz wire coil. The power transmission efficiency was improved from 88.4% to 88.9%. Heat generation from 1 kW power transmission was reduced from 64.3 ℃ to 58.1 ℃.

Failure Mechanism Study of Direct Action Solenoid Valve Based on Thermal-Structure Finite Element Model

Solenoid valves are important electromagnetic devices which are used widely in various fields. Considering the uncertainty of failure mechanisms in practical operation, a thermal-structure coupled model of a direct action solenoid valve is constructed by using the finite element method. The coupled model provides useful information such as temperature distribution and stress distribution for failure mechanism study of the solenoid valve. The model results predict that the failure of the solenoid valve is closely related to the thermal expansion inside the coil, which means the high temperature generated by thermal expansion melts the insulation layers. Under the combined action of high temperature and coupled stress, the shorting of coils occurs and the resistance decreases which may cause the eventual failure of the solenoid valve. To verify the prediction of the finite element model, a degradation experiment is designed. The results suggest that the failure of the solenoid valve is a gradual degradation process, and there are several mutations of coil temperature and resistance. The high temperature melts the insulation layers and causes the shorting of coils, which further decreases the resistance and increases the current. Later more heat is generated to rise coil temperature and melt insulation layers, which will short out the coils and drop the resistance. With such a relationship, as the temperature rises alternately, the resistance decreases alternately until the solenoid valve completely fails. The model provides a reference for failure mechanism study and life prolonging research of solenoid valves.