Insulated Copper Wire Research Articles

Fabric‐Reinforced Functional Insoles with Superior Durability and Antifracture Properties for Energy Harvesting and AI‐Empowered Motion Monitoring

AbstractFunctional triboelectric insoles hold promise for advancing self‐powered wearable technologies. However, their durability is compromised by continuous compressive forces and friction, leading to surface abrasion and material fracturing. To address these challenges, an innovative fabric‐reinforced structure combined with a dual‐L backrest design is developed that enhances anti‐fracture capabilities and electric outputs while enabling AI‐empowered motion monitoring. Polydimethylsiloxane (PDMS) is used as the negative triboelectric material with a dual‐L backrest design, while insulated copper wire (icuW) serves as the positive triboelectric material with an annular structure design. These components are intricately nested to enable a multilayered friction pairing. The fabric‐reinforced structure demonstrates excellent compressive rebound resilience, withstanding forces of at least 1000 N. The functional insole, featuring a fabric‐reinforced dual‐L backrest structure (FRdL‐insole), efficiently harvests biomechanical energy with a peak power of 8214 µW and maintains highly consistent performance after 10 washing cycles and 60 000 durability tests. It can power portable electronic devices such as digital watches, calculators, hygrometers, and LEDs. Enhanced with machine learning algorithms, the FRdL‐insole processes sensor signals to monitor human movements, accurately identifying seven distinct motions. This positions the insole as a smart, real‐time, self‐powered tool for activity recognition, showcasing its potential in intelligent wearable technology.

Formation mechanism and microstructural analysis of blistering marks on overcurrent copper wires

Electrical fires frequently result in severe casualties, with overcurrent faults being a primary cause. This study investigates the formation mechanisms of blistering marks on polyvinyl chloride (PVC) insulated copper wires, traditionally attributed to direct flame exposure. We conducted a comprehensive analysis of PVC copper wires subjected to overcurrents ranging from 190 to 240A, examining the resultant microstructural changes. Our findings challenge conventional beliefs by demonstrating that certain blistering marks, especially on non-flame-retardant PVC (NF-PVC) insulated wires, are indicative of overcurrent faults rather than flame exposure. By integrating detailed microstructural analysis with the thermal decomposition characteristics of the PVC insulation, this study provides new insights into diagnosing the causes of electrical fires and advocates for more meticulous methods in fire investigations.

Dynamic Electrochemical Impedance Spectroscopy for Characterization of the State of Health of Graphite Electrodes

Graphitic carbon is the most used material as anode in lithium-ion batteries since the last 30 years. To make batteries cost-effective for mobility or stationary applications the optimization of every aspect is crucial. Advanced techniques can be implied to undercover or demonstrate the main chemical processes at the graphite electrode such as the Electrochemical Impedance Spectroscopy (EIS). EIS is a powerful technique able to reveal and separate resistive and capacitive properties of an interface in a non-destructive way. It has been applied for the characterization of graphite in order to quantify the charge transfer resistance on the intercalation process, to study the mechanism of formation of solid-electrolyte-interface (SEI), and reveal the lithium plating process [1]. There are high requirements for the collection of impedance spectra on a broad range of frequencies (typically from kHz to tens of mHz) at different electrode potentials regarding measurement time and the condition of a system in equilibrium. To overcome these requirements a technique has been developed called Dynamic Electrochemical Impedance Spectroscopy (DEIS). For DEIS a multi-frequency signal, containing all frequencies to probe in a form of summed sine waves, is superimposed to the galvanostatic current. Using this method, it is possible to measure the time-varying impedance while the system is drifting through non-equilibrium states, e.g. during charge/discharge cycling.In this study we propose DEIS measurements performed on a freshly assembled graphite/lithium half-cell cycled at current rates of C/10 and C/5 and 1C (for aging). Figure 1 A shows the working electrode voltage profile of the first 16 cycles. The chosen geometry for the cell is a three-electrode pouch cell with 2x2cm square electrodes and an insulated copper wire with lithium plated at the tip as micro-reference electrode (see Figure 1 B).The novelty of the proposed method is the fully automatized procedure to acquire the dynamic impedance on a wide frequency band (1kHz-10mHz) continuously over an arbitrary number of cycles to investigate the degradation of the electrode. The experimental set-up is shown as a scheme in Figure 1 C [2]. On base of the recorded current and voltage signals, we computed the time-varying impedance using the Dynamic Multi-Frequencies Analysis (DMFA). This method allows to calculate the impedance at the low frequency band by filtering of the sine components in the Fourier domain; the voltage drift is calculate in the same way [3]. An example of the computed time-varying impedance and the respective potential profile for the first cycle is reported in Figure 1 D.

(Digital Presentation) A Novel Electrochemical Reactor Design-2

(In this design emphasis is given particularly on the tube types of the secondary winding without much change in the previous description of the reactor)Different kinds of energies such as optical, thermal, mechanical etc. are used for carrying out chemical reactions.The following presentation deals with a simple and an innovative idea of utilization of electromagnetic energy for carrying out chemical reactions.Proposed here is an entirely different electrochemical reactor design with an innovative experimental setup which will give - or rather - is very likely to give interesting results while carrying out chemical reactions. The setup is a modified transformer. Unlike the conventional transformer which has a primary and a secondary coil of insulated copper wire wound on a transformer core; this suggested setup has a primary coil of copper, but the secondary coil is in the form of a tube in which a reaction mixture i.e. the reactants can be introduced as shown in Figure 1. Reactants that have at least some electrical conductivity are preferable. If not, provision can be made by adding compatible additives. On applying an alternating sinusoidal electric current in the primary coil; the reactants will directly receive energy by the phenomenon known as mutual electromagnetic induction from the primary coil which will/or should initiate, accelerate or aid the reaction.In the experimental setup we have:1) A primary coil of copper,2) A secondary coil in the form of a tube to carry the reactants,3) Variable frequency and amplitude of the alternating electric current to be applied to the primary coil,4) Type of waveform from the waveform generator,5) Provision to control the rate of flow of the reactants through the tubular secondary coil.By experimenting using the proposed setup, it is very likely that we well get some primary results. Based on these primary results/observations, the setup then can be further tuned down to get the desired results by choosing:1) Number of turns of the primary coil,2) Number of turns of the secondary tube coil carrying the reactants,3) Deciding the frequency, amplitude and the duration of the alternating electric current to be applied to the primary coil,4) Selecting the waveform from the waveform generator,5) Deciding the rate of flow of the reactants through the tubular secondary coil,6) Deciding the material and properties of the tube used in the secondary winding etc.Simultaneously, ultrasound, UV radiation, temperature (either cooling or heating) etc. can also be thought of as an application on the reactants contained in the secondary tube.A catalyst can be coated or inserted at proper locations and in proper shape inside the secondary tube.Different frequencies in a particular sequence and duration can also be applied at the input.The tube of the secondary may be: Transparent,Electrically non-conducting,Electrically conducting with insulation coating from outside,Or a combination of conducting - non-conducting - again conducting as shown in Figure 2,And of any such combinations using two or more types of tubes mentioned above. Such combinations of multiple tube types may prove to be beneficial (e.g. for simultaneous application of UV radiation through the transparent portion) and can be experimented on.Different types of transformer assemblies with secondary in the form of a tube to contain the chemicals can also be used. For example, multiple winding transformers which have two or more primary or secondary windings allowing for different combinations of voltages and current, three phase transformers etc.The reactor can be used to study various types of parameters in different types of chemical reactions such as:1) The study of frequency dependence on the rate of chemical reactions,2) Estimation of triggering frequencies for breaking of bonds in a reaction,3) The threshold of a chemical reaction in terms of frequency can also be tested by application of a triggering pulse at the input etc.Here we have an unusual secondary in a transformer wherein the secondary is a coil of reactants.Experimental validation of the reactor needs to be done which will require a team of experts in chemistry/electrochemistry, transformer designing etc. On reviewing the abstract, should any scientist or a group if scientists find the design intriguing, they are welcome to conduct further research using the proposed reactor design. A provisional patent has been filed for the same. Figure 1

Small Direct Current Electric Motors

When I was about 10 years old, I was given an electric motor kit for Christmas. I had to wind a length of insulated copper wire on the rotor, put together the commutator, and install a small U magnet. I enjoyed the construction experience and with some parental assistance figured out how it worked. Ever since then, I have been curious about these simple artifacts of technology, and this article discusses some of them that I have met in my scientific travels. The small electric motor is a simple piece of technology that is based on mechanics, electricity, and magnetism and is a good mechanism for drawing students into physics.

A C-shaped miniaturized coil for transcranial magnetic stimulation in rodents

Objective. Transcranial magnetic stimulation (TMS) is a non-invasive technique widely used for neuromodulation. Animal models are essential for investigating the underlying mechanisms of TMS. However, the lack of miniaturized coils hinders the TMS studies in small animals, since most commercial coils are designed for humans and thus incapable of focal stimulation in small animals. Furthermore, it is difficult to perform electrophysiological recordings at the TMS focal point using conventional coils. Approach. We designed, fabricated, and tested a novel miniaturized TMS coil (4-by-7 mm) that consisted of a C-shaped iron powder core and insulated copper wires (30 turns). The resulting magnetic and electric fields were characterized with experimental measurements and finite element modeling. The efficacy of this coil in neuromodulation was validated with electrophysiological recordings of single-unit activities (SUAs), somatosensory evoked potentials (SSEPs), and motor evoked potentials (MEPs) in rats (n = 32) following repetitive TMS (rTMS; 3 min, 10 Hz). Main results. This coil could generate a maximum magnetic field of 460 mT and an electric field of 7.2 V m−1 in the rat brain according to our simulations. With subthreshold rTMS focally delivered over the sensorimotor cortex, mean firing rates of primary somatosensory and motor cortical neurons significantly increased (154 5% and 160 9% from the baseline level, respectively); MEP and SSEP amplitude significantly increased (136 9%) and decreased (74 4%), respectively. Significance. This miniaturized C-shaped coil enabled focal TMS and concurrent electrophysiological recording/stimulation at the TMS focal point. It provided a useful tool to investigate the neural responses and underlying mechanisms of TMS in small animal models. Using this paradigm, we for the first time observed distinct modulatory effects on SUAs, SSEPs, and MEPs with the same rTMS protocol in anesthetized rats. These results suggested that multiple neurobiological mechanisms in the sensorimotor pathways were differentially modulated by rTMS.

Multiphysics simulation of an anisothermal reactive spontaneous capillary rise between electric rotor wires

Introduction: The rotor is the mobile component of an electric motor. A wound rotor is composed primarily of a steel core with insulated copper wires wound around it, after which the winding is immersed into a liquid acrylate-based thermosetting resin bath whose role is to ensure the performance and durability of the motor. This impregnation with resin between the wires occurs under controlled temperature settings to facilitate resin flow and polymerization. This process does not involve any pressurization to further facilitate resin flow between the wires; this suggests that, in addition to viscous effects, capillary and gravity forces play a significant role in the impregnation process.Methods: Our ultimate objective is to evaluate the quality of this impregnation. Doing so requires the characterization and simulation of a multi-material and multiphysics process in which heat transfer, polymerization kinetics, and resin flow are strongly coupled. This paper presents a fully coupled macroscopic multiphysics simulation of a unidirectional thermo-regulated capillary rise set-up.Discussion: The modeling choices made produced a good level of agreement with experimental data and enable explanation of a sudden change of regime observed at 120°C, which can be attributed to the polymerization and thermal gradients and their impact on fluid dynamics.

A Novel Electrochemical Reactor Design

To carry out any chemical reaction, normally we require temperature, catalyst, pressure, microwave, ultrasound, UV radiation, help of electrochemistry etc. Proposed here is an entirely different electrochemical reactor design or a different experimental setup which will give or very likely to give interesting results while carrying out chemical reactions or decomposition reactions. The setup is a modified transformer. Unlike the conventional transformer which has a primary and a secondary coil of insulated copper wire wound on a transformer core; this suggested setup has a primary coil of copper but the secondary coil is in the form of a tube in which a reaction mixture or the reactants can be introduced as shown in Figure 1. Reactants having at least some electrical conductivity are preferable. On applying an alternating electric current in the primary coil, the reactants directly will receive energy by electromagnetic induction from the primary winding which will initiate, accelerate or aid the reaction.In the said experimental setup, we have:1) A primary coil of copper,2) A secondary coil in the form of a tube to carry the reactants,3) Frequency and voltage of the alternating electric current to be applied to the primary coil,4) Type of waveform from the waveform generator,5) Rate of flow of the reactants through the tubular secondary coil.By experimenting on the proposed setup, it is very likely that we will get some results, which can be said to be a good sign. The setup then can further be tuned down to get the desired results by choosing the:1) Number of turns of the primary coil,2) Number of turns of the secondary tube coil carrying the reactants,3) Deciding frequency, voltage and duration of the alternating electric current to be applied to the primary coil,4) Selecting a waveform from the waveform generator,5) Deciding the rate of flow of the reactants through the tubular secondary coil,etc.Simultaneously ultrasound, UV radiation, temperature etc. can also be applied on the reactants contained in the secondary tube coil if so required.Catalyst can be inserted at proper locations and in proper shape inside the secondary tube in such a way that the flow of the reactants is not hindered.The threshold of a chemical reaction in terms of frequency can also be tested by application of a triggering pulse at the input.Different types of transformers, with the secondary in the form of a tube to contain the chemicals, can also be used. For example, multiple winding transformers which have two or more primary windings allowing for different combinations of voltages and currents, three phase transformers, toroidal core transformers, air core transformers etc.The above explained system can also be used in flow microreactors and in continuous flow chemistry.The circuit of the secondary is completed as shown in the figure.Here we have a strange/unusual secondary in a transformer wherein the secondary is of flowing nature and interestingly of flowing reactants.In this reactor the EMF is generated directly in the reactants contained in the secondary coil which will force electrons to move thereby initiating, accelerating a reaction.The tube of the secondary may be transparent or non-conducting or conducting with insulation coating from outside.Experimental validation of the proposed electrochemical reactor has to be done and will require experts in electrochemistry, transformer designing etc. I have many limitations in performing the further work. On reviewing the abstract and the figure, if any scientist or a group of scientists finds the design intriguing, they are welcome to do further research using the proposed reactor design. A provisional patent has been filed for the same.The main purpose of submitting this abstract/write-up to the conference is to present before the scientists of the electrochemical society an entirely different electrochemical reactor design. Figure 1

Analysis of heat transfer during flame spread over energized-wire under high currents

Electrical wire is one of the primary causes of electrical fires because of short circuiting or overload current. Experiments were carried out to characterize the influence of high currents on flame spread and dripping behaviors over wires. Two samples of polyethylene (PE)-insulated copper wires with different sizes (dc/do = 0.9 mm/3.0 mm for wire #1 and 1.3 mm/4.2 mm for wire #2) were electrified with current, ranging from 10 A to 50 A, to conduct experimental study. Results show that the dripping becomes faster as the current increases and the continuous dripping occurs under high current (I > 40 A for wire #1 and I > 30 A for wire #2), causing the flame to be narrower and shorter. The heat transfer by different passages (radiation, convection, conduction through core and the joule heat) were quantitatively analyzed. The heat feedback from core to the insulation (q˙cp) were the dominant heat transfer mode during flame spread over energized wire. Heat required for flame spread (q˙req) is mainly supplied from the core, nearly 80%, including the joule heat (q˙joule) and the heat conduction through the core from the burning zone (q˙cc). The proportions q˙cp/q˙req decreased with the increasing current, and has a sharp decent to 70% or 50% at I = 50 A or 35 A for wire #1 or wire #2, respectively. In addition, the proportion of q˙cp to the sum of q˙joule and q˙cc drops obviously under high current, which means the dominated role of core heat feedback in heat transfer mode is weakened under high current. A flame spread model for energized wire based on the quantitative analysis of controlling heat transfer mechanism was proposed, and it predicted the flame spread rate well within error of ±20%. The findings of the presented study will be essential for simulation study of flame spread behavior over energized wires with high current and may guide the design of future electric fire safety.

Expanding a single‑lead mobile electrocardiographic device to multiple‑lead recordings improves diagnostic accuracy and confidence

BackgroundMobile electrocardiographic (mECG) devices that record ECG lead I have been used to detect atrial fibrillation. Other arrhythmias may not be readily diagnosed with one lead. Obtaining multi‑lead tracings from an mECG (MLmECG) to simulate a 12‑lead ECG may lead to more accurate diagnoses. MethodsWe developed a method to generate multi‑lead ECGs using a mECG device by attaching it with alligator clips connected to an insulated copper wire to adhesive electrodes on the patient's limbs and torso according to standard lead configurations. Different rhythm and conduction abnormalities from a sample of inpatients were collected. Arrhythmias were recorded in three ways (single lead, MLmECG, and standard 12‑lead) and grouped by category. Recordings were sent to cardiology fellows in the form of a multiple choice survey. Participants were asked for their diagnosis and confidence in their decision. ResultsSurvey response rate was 100%. Single‑lead, MLmECG, and 12‑lead yielded 48.2%, 81.6%, and 88.6% of agreement with the correct diagnosis, respectively (single‑lead vs. MLmECG or 12‑lead; p < 0.01). Overall mean confidence scores were 3.34, 4.35, and 4.53 out of 5, for single‑lead, MLmECG, and 12‑lead ECG, respectively (single‑lead vs. MLmECG or 12‑lead; p < 0.01, MLmECG vs. 12‑lead; p = 0.09). ConclusionThe diagnostic accuracy of MLmECGs were similar to that of a standard 12‑lead ECG. Fellows' confidence in their diagnosis were similar between MLmECG or 12‑lead ECG, and higher with both modalities compared to a single‑lead tracing. The ability to recreate, as fully as possible, a standard 12‑lead ECG is a reasonable goal for mobile technology.

A 20-gauge active needle design with thin-film printed circuitry for interventional MRI at 0.55T.

This work aims to fabricate RF antenna components on metallic needle surfaces using biocompatible polyester tubing and conductive ink to develop an active interventional MRI needle for clinical use at 0.55 Tesla. A custom computer numeric control-based conductive ink printing method was developed. Based on electromagnetic simulation results, thin-film RF antennas were printed with conductive ink and used to fabricate a medical grade, 20-gauge (0.87 mm outer diameter), 90-mm long active interventional MRI needle. The MRI visibility performance of the active needle prototype was tested in vitro in 1 gel phantom and in vivo in 1 swine. A nearly identical active needle constructed using a 44 American Wire Gauge insulated copper wire-wound RF receiver antenna was a comparator. The RF-induced heating risk was evaluated in a gel phantom per American Society for Testing and Materials (ASTM) 2182-19. The active needle prototype with printed RF antenna was clearly visible both in vitro and in vivo under MRI. The maximum RF-induced temperature rise of prototypes with printed RF antenna and insulated copper wire antenna after a 3.96 W/kg, 15 min. long scan were 1.64°C and 8.21°C, respectively. The increase in needle diameter was 98 µm and 264 µm for prototypes with printed RF antenna and copper wire-wound antenna, respectively. The active needle prototype with conductive ink printed antenna provides distinct device visibility under MRI. Variations on the needle surface are mitigated compared to use of a 44 American Wire Gauge copper wire. RF-induced heating tests support device RF safety under MRI. The proposed method enables fabrication of small diameter active interventional MRI devices having complex geometries, something previously difficult using conventional methods.

Effect of welding parameters on resistance thermocompression microwelded joint of insulated copper wire

Insulated copper wire has been widely used in many industries, but the insulating coating must be removed before welding because it will hinder the formation of joints. Therefore, in this work, the resistance thermocompression microwelding process for insulated wire without removing the coating in advance was proposed. Through detailed mechanical testing and metallurgical examination, the effects of welding voltage on the joint appearance, joint macro-/microstructure, joint breaking force, and joint fracture mode were investigated. The results showed that joints were achieved by solid-state bonding. As the welding voltage was further increased, the joint breaking force increased first and then decreased. Corresponding to the change of the welding voltage, the fracture mode of the joints changed from interfacial fracture to partial pullout fracture. The fracture position also moved backwards gradually, which was caused by the expansion of the bonding area, the improvement of the interfacial strength, and the amount of heat input. Finally, an orthogonal experiment was conducted to investigate the significance level of three parameters. Under the optimal for joint breaking force parameters (2.1 V, 24 ms, and 12 N), the average achievable force was 1.1723 N, which was about 83.7% of the breaking force of the as-received wire.

Experimental Study on the Thermoplastic Dripping and Flame Spread Behaviors of Energized Electrical Wire under Reduced Atmospheric Pressure.

Flame spread over wire surface is different from other solid fires as it is usually accompanied by melting and dripping processes. Although the related behaviors at reduced pressure (20–100 kPa) are significant to those fire risk evaluations, very few studies have been undertaken on this matter. Therefore, the thermoplastic dripping and flame spread behaviors of energized polyethylene insulated copper wires were investigated experimentally at reduced pressure. It was known from experimental results that the dripping frequency increases, showing a relatively smooth (linear) and rapid (power) increasing trends under high and low electrical currents, respectively. A short-period flame disappearance was observed during the dripping process, which is unique for the energized wire at reduced pressure. The bright flame can disappear for several seconds and then show again after the dripping. While at 20 kPa or lower, the wire flame would turn to a completed extinguishment after the dripping. A critical dripping point was proposed to show the minimal required electrical current to sustain the flame spearing. The critical current changes smoothly during 100–80 kPa and decreases rapidly at 80–60 kPa. Additionally, the dripping phenomenon can stop or delay the flame spread, partly because of the short-term flame disappearance.

Stainless-Core Submersible Permanent Magnet Synchronous Machine

A fully submersible permanent magnet synchronous machine (PMSM) is introduced in this paper. Underwater operation requires that the machine parts have to be resistant to corrosion, and the electrically conducting parts need to be properly insulated from water. The machine under study consists of a rotor-surface permanent magnet rotor, protected by a glass-fiber-reinforced plastic (GFRP) cover, and a fully stainless stator. The novelty of the machine is found in the design and special materials used in the manufacture. The stator core is made of ferritic stainless steel laminations, and the selected winding material is polyvinyl chloride (PVC) insulated copper wire. An extra low-speed, stainless-core submersible PMSM was constructed and tested. To simplify the machine construction, a tooth-coil single-layer winding was adopted. An asymmetric stator design was selected to enhance the machine performance. The performance of the 1.7 kW, 80 r/min machine was analyzed by finite element analysis (FEA) and validated by experimental tests, where despite a very low rotational speed, 74% efficiency was reached at the target load point. The PMSM was found to be fully functional for the application.

Optimisation of an in-process lineal dielectric sensor for liquid moulding of carbon fibre composites

A dielectric sensor appropriate for process monitoring of carbon fibre composites manufacturing has been optimised and implemented in Resin Transfer Moulding (RTM). The sensor comprises a pair of twisted insulated copper wires and can be adapted to monitor both flow and cure. To simulate the dielectric response of the sensor, an electric field model was developed. The model was coupled with a multi-objective optimisation genetic algorithm to optimise the sensor design. The optimisation showed that increasing wire radius and decreasing coating thickness increases sensor sensitivity. Different sensor designs were implemented and used in a series of RTM trials to validate the technology in industrial conditions. The selelcted sensors operated successfully at pressures up to 7 bar and temperatures up to 180 °C. A low diameter sensor using copper wire coated with polyimide showed the best response monitoring flow with an accuracy of 95%, whilst also following the cure and identifying vitrification.

Effect of reduced ambient pressures and opposed airflows on the flame spread and dripping of LDPE insulated copper wires

The effect of ambient pressure on flame spread and insulation dripping of copper-cored, LDPE-insulated wires exposed to opposed airflows was investigated to increase understanding of electrical wire fire hazards in spacecraft environments. Utilized wire samples consisted of 0.64 mm-diameter copper cores surrounded by 4 mm-outer diameter LDPE insulation sheaths. The wire characteristics were selected for comparison with future experiments planned in the International Space Station (ISS) with similar wires. Environmental pressure was varied from sub-atmospheric (40 kPa) to atmospheric (100 kPa). Wires oriented horizontally were exposed to opposed airflows with speeds of 10 or 20 cm/s. Results showed that flame spread rates increase with pressure and decrease with increasing opposed flow speeds. Melted and burning insulation left behind by flame spread dripped with a frequency that increased with pressure; the total mass dripped decreased with pressure. It was also found that lower flows produced more frequent dripping with less total mass dripped, and higher flows produced the opposite. Coincidingly, as the mass of dripped insulation increased, the flame spread rate decreased. Comparison of present results with those from studies with different wire samples show that the effect of environmental parameters on flame spread and insulation dripping depends strongly on core conductivity and core/insulation diameters. Consequently, care should be taken in extending results obtained from specific wire tests to other wires without justification.

Experimental study on thermal and fire behaviors of energized PE-insulated wires under overload currents

The electric fires are highly likely caused by the combustible wire insulation material ignited by a short circuiting or overload current in residential and commercial buildings, nuclear power plants, etc. It is important to know fire behaviors of the insulation materials over energized wires under overload currents, so fire behaviors are investigated experimentally over high-current energized polyethylene (PE)-insulated copper wires A and B with different sizes (dc/do = 0.9 mm/3.0 mm and 1.3 mm/4.2 mm for wires A and B, respectively, where dc and do denote the core and outer diameter of wire, respectively). The results show that the flame height rises firstly and then remains steady with the increasing current under low current, which is similar with the previous research, while the flame height drops sharply when the current is extremely high over 40 A. The flame width also drops with current under high-current condition. In addition, the surface temperature of wire, measured by infrared thermography, agrees well with the predicted balance temperature of wire under low current, but deviates from the balance temperature under high currents. Correspondingly, the measured flame spread rate agrees well with the prediction model based on the thermal balance temperature at low currents, while shows an obvious deviation under large currents. The flame spread rate grows approximately with the square of the current, but tends to increase slowly and even remains steady under high current. Moreover, the effects of wire size on flame spread are also investigated. The flame of wire with large diameter is wider, but its flame spread rate is lower and rises slower with current. The results of this work provide important information about fire behaviors over energized wires under overload currents and may guide the design of future electric fire safety.

Effects of electric current and sample orientation on flame spread over electrical wires

Electrical wire is one of the primary causes of electrical fires. Experiments were conducted to study the effects of electric current and sample orientation on flame spread over polyethylene (PE) insulated copper wires. The flame spread velocity showed a non-monotonic trend with the inclination angle, i.e., the flame spread velocity firstly decreased and then increased with the increasing inclination angle. In the upward flame spread configuration, the molten polymer flew down along the wire if the wire was inclined, which resulted in a periodic flame spread phenomenon, and a sub-flame was observed behind the primary flame. The periodic time was shorter for the smaller inclination angle or the lower electric current. The downward spread seemed to be more susceptible to the electric current. A flame spread model considering the effects of inclination angle and electric current was developed. The heat transfer analyses in the preheating region were conducted to study the controlling mechanism of flame spread.

Skinning of Insulated Copper Wires within the Production Chain of Hairpin Windings for Electric Traction Drives

Skinning of Insulated Copper Wires within the Production Chain of Hairpin Windings for Electric Traction Drives

MRI-based transfer function determination through the transfer matrix by jointly fitting the incident and scattered field.

PurposeA purely experimental method for MRI‐based transfer function (TF) determination is presented. A TF characterizes the potential for radiofrequency heating of a linear implant by relating the incident tangential electric field to a scattered electric field at its tip. We utilize the previously introduced transfer matrix (TM) to determine transfer functions solely from the MR measurable quantities, that is, the B1+ and transceive phase distributions. This technique can extend the current practice of phantom‐based TF assessment with dedicated experimental setup toward MR‐based methods that have the potential to assess the TF in more realistic situations.Theory and MethodsAn analytical description of the B1+ magnitude and transceive phase distribution around a wire‐like implant was derived based on the TM. In this model, the background field is described using a superposition of spherical and cylindrical harmonics while the transfer matrix is parameterized using a previously introduced attenuated wave model. This analytical description can be used to estimate the transfer matrix and transfer function based on the measured B1+ distribution.ResultsThe TF was successfully determined for 2 mock‐up implants: a 20‐cm bare copper wire and a 20‐cm insulated copper wire with 10 mm of insulation stripped at both endings in respectively 4 and 3 different trajectories. The measured TFs show a strong correlation with a reference determined from simulations and between the separate experiments with correlation coefficients above 0.96 between all TFs. Compared to the simulated TF, the maximum deviation in the estimated tip field is 9.4% and 12.2% for the bare and insulated wire, respectively.ConclusionsA method has been developed to measure the TF of medical implants using MRI experiments. Jointly fitting the incident and scattered B1+ distributions with an analytical description based on the transfer matrix enables accurate determination of the TF of 2 test implants. The presented method no longer needs input from simulated data and can therefore, in principle, be used to measure TF's in test animals or corpses.