Low Conductor Research Articles

Common mode far field radiation mechanisms and prediction of a buck converter with cables based on common mode voltage mutation method

AbstractIn the field of electromagnetic compatibility (EMC) research, the knowledge of the formation mechanism of the far field electromagnetic radiation and its prediction is essential for the electromagnetic noise suppression design of a switched mode power supply. This paper investigates the equivalent driving sources of the common mode (CM) current of a Buck converter with cables. Based on the concept of CM voltage mutation, this paper proposes two mechanism models of the same‐direction CM voltage driving mode and the opposite‐direction CM voltage driving mode and derives the approximate analytical formulas for the far field intensity estimation of the horizontal cables. To evaluate the predictive effectiveness of the CM far field radiation model, a 30 MHz very high frequency (VHF) Buck prototype with shielded cables is built and tested, and a shielding shell and low impedance ground conductor suppression designs are then verified. The CM electromagnetic radiation mechanisms of a non‐isolated power converter are demonstrated here. The proposed electromagnetic radiation models, approximate analytical formulas, and improvement design can help to advance the CM radiation analysis and optimization design.

An insight into the effect of carbon nanofillers in glass fibre epoxy nanocomposites through dielectric spectroscopy

Interfacial characteristics of nanocomposites are critical limiting factors in the design of polymer nanocomposites. The nanocomposites have complex structures and play a pivotal role in controlling functional properties. Analysis of interfacial layers in polymer nanocomposites, existing between the polymer matrix and the nanoparticles plays a major role in determining their characteristics. High-frequency analysis of electrical conductivity and dielectric properties of carbon nanofillers which are embedded in an epoxy matrix were analysed using alternating current dielectric spectra. This article provides a correlation between the electrical transport properties and dielectric behaviour of epoxy carbon nanocomposites at different temperatures are investigated with variations in frequency. Electrical transport properties of nanocomposites are primarily dictated by electron tunnelling and matrix, nanofillers conductivity. Dielectric spectroscopy in the frequency range 10 Hz–8 MHz has been performed on epoxy nanocomposites with and without hybrid carbon nanofillers at one weight percentage (2:3 ratio). Dominant dielectric relaxation mode is observed in the base composite at a low-frequency region (≥10 Hz), whereas nanocomposite with hybrid carbon nanofillers is observed to induce two dielectric relaxations in the kHz region. Increase in non-monotonic variations in dielectric spectra makes the nanocomposite suitable for high temperature low sag conductor core, aerospace and cryogenic engineering applications.

Fast Quench Propagation Conductor for Protecting Canted Cos-Theta Magnets

Canted Cos-Theta (CCT) magnet design offers remarkable advantages such as a low number of parts and the ability to intercept with the formers the Lorenz forces acting on the windings. However, by principle, it is very challenging to design a self-protected CCT magnet, even with relatively low stored energy and conductor current density. This is predominantly due to the normal zone being unable to propagate along the magnet axial direction. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fast Quench Propagation Conductors (FQPCs) for quench protection of CCT magnets are proposed and studied. FQPC is a superconducting conductor carrying the magnet transport current and placed along the main axis of the CCT magnet in good thermal contact with the turns of the windings. FQPC is connected electrically in series with the CCT windings but electrically insulated at the thermal contacts by the electric insulation of the conductors. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">The FQPCs aim to spread the normal zones in the CCT windings via a shorter axial path rather than only the path along CCT conductors and between them in the formers channels. Typically, ribs of the former inhibit axial quench propagation, and the FQPCs thermally connect CCT windings in the axial direction. The FQPCs quench due to the heat generated in the quenched turn and then act effectively like quench heaters powered by the magnet current. It means a completely passive system powered by the magnet energy that becomes inactive after magnet current decay. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Quench protection transients are calculated using a consecutive-simulation approach involving two software tools developed as part of the STEAM framework at CERN: a finite element (FE) based tool called FiQuS coupled with a finite difference (FD) based tool called LEDET. This approach allows for a three-dimensional (3D) quench simulation and introduces a great level of geometrical detail while maintaining a reasonable computational effort. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">The benefits of the FQPCs depend on their number, placement, and duration of quench transient, which is affected by the CCT magnet size. These dependencies are studied in terms of the winding maximum temperature and voltage-to-ground that result from single, hot-spot-induced quenches in various locations in the windings.

Dynamic mechanical analysis for assessment of carbon fillers in glass fiber epoxy composites

AbstractThe effect of incorporation of micron sized aluminum trihydrate, multi‐walled carbon nanotubes, and graphene nano platelets into glass fiber reinforced epoxy matrix is investigated using dynamic mechanical analysis. The objective of the investigation was to develop polymer central core of high temperature low sag transmission conductor. The effect of individual and hybrid carbon fillers on the viscoelastic properties of the epoxy composites is investigated and discussed. The storage modulus of the glass reinforced epoxy increases by 20% at room temperature due to incorporation of carbon nanofillers. In glass transition region, the increase is higher between 40% and 60% and it varies up to 90% in the rubbery region. Key attributes of carbon filler addition are limited enhancement of storage modulus at room temperature, higher enhancement over glassy, glass transition, and rubbery regions. The carbon fillers extend the temperature range of the glassy region. The cross‐link density, filler efficiency, and degree of entanglement of fibers are estimated to understand the implications of the carbon fillers on the viscoelastic properties. The loss modulus peak of glass epoxy composite increases from 2800 to 3900 MPa with carbon fillers and the increase in glass transition temperature is 47°C. Incorporation of carbon fillers leads to increase of damping factor peak from 0.2 to 0.28. Cole–Cole plots have established the inherent heterogeneity of epoxy systems due to the presence of carbon fillers. Prediction models for storage modulus and damping factor have been proposed to highlight the influence of geometry and size of carbon filler.

High Electrical Conductivity and Low Temperature Resistant Double Network Hydrogel Ionic Conductor as a Flexible Sensor and Quasi‐Solid Electrolyte

AbstractThe existence of large amounts of water in hydrogel electrolytes makes them inevitably freeze at low temperatures, which causes them to lose properties such as flexibility or electrical conductivity. It limits the application of hydrogel electrolytes at low temperatures. Here, we designed hydrogels with interpenetrating double network structure based on polyacrylamide and agar. By doping a high concentration of LiCl as the conducting material, a continuous ion‐conducting path was formed. The conductivity reached 2.18 S/m at 25 °C and 1.58 S/m at −30 °C. The prepared hydrogel electrolytes exhibit good mechanical and electrochemical properties to meet the needs of different application situations. A wearable sensor with hydrogel electrolytes was demonstrated. The wearable sensor can be attached to a part of the human body and can successfully detect various human movements. The wearable sensors can be used as temperature sensors in addition to detecting motion, which shows an encouraging and powerful utility in wearable electronic devices.

Highly Stretchable, Self-Healing, and Low Temperature Resistant Double Network Hydrogel Ionic Conductor as Flexible Sensor and Quasi-Solid Electrolyte.

With the rapid development of flexible energy storage and wearable strain sensing, conductive hydrogels are attracting attention as electrolyte materials for flexible strain sensors and flexible supercapacitors due to their excellent flexibility and wetting properties. In this work, antifreezing hydrogels with high stretchability, adhesion, and conductivity are designed and prepared by introducing phosphoric acid solutions into polyacrylamide and chitosan systems. The multifunctional hydrogel samples prepared by this method can be used as both quasi-solid electrolytes and wearable strain sensors. The hydrogel-based supercapacitor shows a charge/discharge efficiency of 99.67% and a capacitance retention of 98.85% after 10000 cycles charge/discharge tests at -30°C. The tiny characteristic heartbeat wave forms are detected by the hydrogel as a flexible strain sensor. It is foreseeable that PCP multifunctional hydrogel can be a promising flexible material for a new generation of flexible sensors and flexible energy storage devices in a certain range of temperatures.

Current sharing and stability in an extremely low AC-loss MgB2 conductor

In the push to develop high power electric aircraft, superconducting technology promises to significantly reduce mass and volume of motors and generators. However, challenges related to AC-loss and thermal management are a significant factor in preventing the proliferation of aerospace superconducting technologies. Increasing the resistance of the metal matrix stabilization has only gone so far in reducing coupling currents for higher frequency applications. In this research, Multiphysics simulations of a single composite filament were used to investigate stability decreases when using very high thermal conductivity electrical insulator (CsI) or metal-to-insulator transitioning material (V2O3) to replace the slightly resistive metal matrix typically used for a low AC loss MgB2 composite wire. The insulators separate the MgB2 filaments entirely, only allowing transient current sharing to occur with the high purity Nb diffusion barrier or with the metallic state V2O3. These simulations show that for these very low AC-loss composites at 20 K, instability will become a major issue due to reductions in current sharing. With higher electrical conductivity metal-to-insulator materials, higher thermal conductivity impregnation materials, and thicker metallic diffusion barriers it may be possible to find a reasonable balance between AC-loss and stability.

Design and analysis of a super wideband (0.09[formula omitted]30.14 THz) graphene based log periodic dipole array antenna for terahertz applications

A micro-scaled printed log periodic dipole array (LPDA) antenna is proposed for terahertz (THz) applications. The proposed low profile graphene conductor based LPDA antenna is designed with integrated protudent dipoles to realize super wide bandwidth and high gain characteristics. The suggested THz antenna is designed on a 10 µm thick Rogers RT / Duroid 5880 ™ substrate material of dimension 450 µm × 500 µm. The proposed antenna exhibits 2:1 VSWR operating super wide bandwidth (SWB) of 30050 GHz (0.09–30.14 THz) with a peak gain of 16.02 dBi. The designed antenna shows fractional bandwidth of 199.46% along with a huge bandwidth ratio of 334.88:1. The radiation efficiency balancing from 85% to 98.2% is maintained throughout the whole operating –10 dB SWB (0.09–30.14 THz). Design formulation of the proposed structure, structural parametric analysis, surface current distribution and characteristics parameters are discussed in detail in this paper. The proposed antenna covers the entire frequency band of the terahertz region to support a number of sub-terahertz and terahertz communication applications such as high speed short distance communication, video rate imaging, biomedical imaging, surveillance, mine detection, sensing, and security scanning.

A low profile artificial magnetic conductor based tri‐band antenna for wearable applications

AbstractA wearable flexible tri‐annular square ring monopole antenna with artificial magnetic conductor (AMC) is proposed. The antenna operates at the ISM band (2.28–2.51 GHz, 5.2–6 GHz) and at WiMAX band (3.5‐4GHz) for wireless body area network (WBAN) applications. The number of antenna operating bands is determined by the number of square rings. A tri‐band AMC array is integrated to reduce the specific absorption rate (SAR) and the antenna profile. The overall size of antenna with AMC array is 90 × 90 × 6 mm3. The peak gain of the antenna is 4.8, 5.1, and 6.2 dBi at three frequency bands, respectively. The proposed antenna and AMC were printed on a flexible polyimide film. The antenna has good conformity, easy processing, lightweight and low profile of 0.048 λ0 at 2.4 GHz. The antenna was fabricated and measured where a very good agreement between simulated and measured results for S11 and radiation pattern. The measured antenna radiation efficiency is more than 70% in the operating frequency band.

A Circularly Polarized 3-D Printed Dielectric Transmitarray Antenna at Millimeter-Wave Band

In this letter, a novel elliptical cylinder dielectric resonator (ECDR) is proposed. By combining a square substrate and two symmetrical ECDRs, an ECDR element is formed, which can effectively achieve the transformation from the linearly polarized incident wave to the circularly polarized (CP) transmitted wave. By adjusting the height of the element, a linear transmission phase range over 360° can be obtained, which can reduce the fabrication difficulty and cost through a 3-D printed technology significantly. Meanwhile, the ECDR element has a low conductor loss in high frequency. Additionally, a CP 3-D printed dielectric transmitarray antenna at the millimeter-wave band is designed by employing the ECDR elements. It is found that the aperture efficiency is up to 40.3%, the 3 dB axial ratio bandwidth is 17%, and the 1 dB gain bandwidth is 13.3%, respectively. The measured results are in good agreement with the simulated ones. This may be the first time that a CP 3-D printed dielectric transmitarray antenna has been reported.

Stretchable gold nanowire-based cuff electrodes for low-voltage peripheral nerve stimulation

Objective. Electrical stimulation of the peripheral nervous system (PNS) can treat various diseases and disorders, including the healing process after nerve injury. A major challenge when designing electrodes for PNS stimulation is the mechanical mismatch between the nerve and the device, which can lead to non-conformal contact, tissue damage and inefficient stimulation due to current leakage. Soft and stretchable cuff electrodes promise to tackle these challenges but often have limited performance and rely on unconventional materials. The aim of this study is to develop a high performance soft and stretchable cuff electrode based on inert materials for low-voltage nerve stimulation. Approach. We developed 50 µm thick stretchable cuff electrodes based on silicone rubber, gold nanowire conductors and platinum coated nanowire electrodes. The electrode performance was characterized under strain cycling to assess the durability of the electrodes. The stimulation capability of the cuff electrodes was evaluated in an in vivo sciatic nerve rat model by measuring the electromyography response to various stimulation pulses. Main results. The stretchable cuff electrodes showed excellent stability for 50% strain cycling and one million stimulation pulses. Saturated homogeneous stimulation of the sciatic nerve was achieved at only 200 mV due to the excellent conformability of the electrodes, the low conductor resistance (0.3 Ohm sq−1), and the low electrode impedance. Significance. The developed stretchable cuff electrode combines favourable mechanical properties and good electrode performance with inert and stable materials, making it ideal for low power supply applications within bioelectronic medicine.

Parametric FEM modeling of multilayer castellated canted cosine theta (CCT) magnets

Canted cosine theta (CCT) magnets have received increased attention in the recent years due to their inherent characteristics of high field quality and low conductor stresses, as each turn is supported by the metallic former. CCT geometry is suitable for complex magnets—such as nested dipoles, which allow full 360° control of the magnetic field direction. Modeling and design of such magnets is the subject of this work. A parametric 3D modeling framework for multilayer CCT magnets has been developed and optimized allowing efficient model generation without a need for both: CAD software and time consuming meshing. The model has been created using the APDL scripting language and solved using the Ansys software. By direct generation of nodes and elements the time to generate a model with one million elements was of the order of 10 min. A framework for script generation was developed, as well as the relations between the mesh parameters and the total number of nodes and elements. Detailed mesh dependence study was carried-out with in-depth analysis of solver performance (solution time, amount of written data, RAM requirements). Global and local convergence criteria were introduced to find the optimal mesh size. The case of a four layer 2.5 Tm nested dipole was analyzed in details including the worst-case scenario with full debonding between the CCT layers. Thanks to the castellations the nested-dipole is safe to support 144 000 Nm of torque due to Lorentz forces even with full de-bonding between the layers.

A Review on Utilization of Plastic Wastes in Making Construction Bricks

Plastic waste is spread at an unprecedented speed due to the rapid use of domestic and industrial plastic items. The environmental pollution resulting from the continued disposal of plastic wastes in landfills has not only created land problems but has also heightened the pollution of marine resources. This paper aims to review and investigate the feasibility of utilizing plastic waste in making construction bricks. The use of plastic waste in making the sand-plastic bricks will enhance the protection of the environment from the effects of plastic waste that normally takes several millennials to degrade. Thermostatic plastic waste; that is, those polymers whose recycling may not affect the environment, including polyethylene (PE) and polyethylene terephthalate (PET), is found to implore lightweight, durable, cost-effective, and low thermal conductor bricks. Compressive strength (CS) and water absorption tests are found as the key test methods for measuring the effectiveness of high-volume content of plastic waste in bricks. Notably, a high percentage of plastic waste in proportion to sand is found to improve the compressive strength of the bricks besides allowing negligible water to seep through.

Optimization Design of Oil-Immersed Iron Core Reactor Based on the Particle Swarm Algorithm and Thermal Network Model

In this paper, according to the design parameters of oil-immersed iron core reactor, the thermal network model of windings is established by the thermo-electric analogy method, and the temperature distribution of the windings can be obtained. Meanwhile, a fluid-thermal coupled finite element model is established, the temperature and fluid velocity distribution are extracted, and the simulation results show that the error coefficient of temperature is less than 3% compared with the thermal network model, so the correctness of thermal network model has been verified. Taking the metal conductor usage and loss of windings as the optimization objects, the optimization method based on the particle swarm algorithm and thermal network model is proposed, and the Pareto optimal solutions between the metal conductor usage and loss of windings are given. The optimization results show that the metal conductor usage is reduced by 23.05%, and the loss is reduced by 20.25% compared with the initial design parameters, and the maximum temperature of winding does not exceed the expected value. Thus, the objects of low metal conductor usage and loss of windings are conflicted and cannot be optimized simultaneously; the optimization method has an important guiding significance for the design of oil-immersed iron core.

Incidence of corrosion in low voltage electrical conductor

This research used a salt spray booth to generate accelerated corrosion in a copper conductor, AWG 12-gauge purity of 95.95%, this caliber used in residential electrical installations according RETIE Chapter 3 Article 20 and NTC 2050 338. Additionally, to provide an enabling stage of corrosion, type mouse tail splices were made. The amount of corrosion is measured by weight loss, and incidence of corrosion in transport was evaluated from two perspectives: difference active at the beginning and end of the test power, and the change in resistance of the specimen measured at different times of the experiment. The test piece was subjected to a flow of alternating current into a low voltage system, while corrosion occurred. Using two single-phase two-wire electronic meters, the rate of power supply circuit test was recorded, to check for changes in the energy carried from exposure to the corrosive environment wire. The data collected showed that exposure times of the samples in the salt spray chamber involvement was not very noticeable in the copper wire, highlighting small corrosion spots. Similarly, the energy no changes were observed to induce corrosion, however, the resistance of the wire showed a total change of up to 2.4 [milliohms]. The data collected showed that exposure times of the samples in the salt spray chamber involvement was not very noticeable copper wire, highlighting small corrosion spots. Similarly, the energy no changes were observed to induce corrosion, however, the resistance of the wire showed a total change of up to 2.4 [milliohms].

Conductor sag comparison for 132 kV overhead transmission line improvement in Malaysia

This paper presents conductor sag comparison for 132 kV overhead transmission line improvement in Malaysia. Increasing industrialization and population growth around the world demands higher electricity supply. Power generation has yet to decline but transmitting sufficient electricity to consumers is worrisome due to scarce land space occupied by rapid urbanization. Hence reconductoring method was chosen to improve existing 132 kV overhead transmission line in Malaysia. A group of selected conductors were chosen for comparison where the high temperature low sag conductor stood out the most producing up to 40% sag reduction. This paper focuses on providing conductor alternatives to improve maximum sag of lowest conductor to ground for 132 kV transmission line in Malaysia in accordance to her climate and geographical factor.

Absorbing Elements Based on a Uniform Resistive Film for the Implementation of a Wide Range of Radio Signal Power Attenuations

Rectangular and complex-shaped absorbing elements based on a uniform resistive film are used for constructing waveguide, coaxial, and microstrip attenuators. A decrease in the attenuator’s dimensions leads to difficulties in the implementation of low and high attenuations, which requires passing to absorbing elements based on piecewise uniform structures. In this work, topologies of small absorbing elements of the waveguide, coaxial, and microstrip attenuators are proposed to implement a wide range of radio signal power attenuations. They differ from the known elements of attenuators with a two-layer resistive film in terms of their lower temperature stability and sophisticated manufacturing technology. Such attenuation is achieved by using a single-layer resistive film with a central region having a high (cut) or low (conductor) specific resistance. A technique based on the rigorous method of conformal mappings for calculating the proposed absorbing elements is developed. In the considered particular cases, the obtained relations coincide with those known in the literature. Three-dimensional plots of radio signal power attenuation and normalized input resistance as functions of the normalized size of the cut or conductor of the central region are presented. A broad range of possibilities of the control for output parameters of absorbing elements are outlined. The working capacity of the technique is verified by modeling both the equivalent circuit parameters and output parameters of the absorbing elements, namely, input resistance and attenuation, as well as by the analysis of real samples of small add-on absorbing elements of microstrip attenuators with the proposed topologies. The modeling is carried out in the Russian Elcut software package.

Current Distribution in Conduction-Cooled NbTi/BSCCO Composite Conductor

In this paper, an NbTi/BSCCO composite conductor made of NbTi/Cu wire and BSCCO/Ag wire cooled by cryocooler were investigated, extending the basic research on current distribution characteristics of low temperature superconductor and high temperature superconductor composite conductor and exploring its potential application. Current distribution characteristics with operating current, temperature, magnetic field, and current frequency were simulated and measured. Current-transfer characteristics between the two superconductors were also obtained.

A Wideband E-plane Pattern Reconfigurable Antenna with Enhanced Gain

A novel method of steering antenna beam in its E-plane is introduced and a design of wideband pattern reconfigurable antenna with enhanced gain is proposed in this paper. A bowtie antenna is used as the driven radiator, and two parasitic bowtie-shaped microstrip stubs with two diodes are loaded beside each arm of the driven radiator. With the introducing of a low profile artificial magnetic conductor (AMC) beneath the bowtie radiator, unidirectional radiation pattern can be obtained. By altering the working states of the diodes, the main beam of the antenna can be switched in its E-plane. The biasing circuit of the antenna is simple and easy to be implemented. The prototype of the antenna is fabricated, and good agreement can be observed between the simulated and measured results. Compared to other pattern reconfigurable antennas, the proposed antenna has advantages of a wide operating band, ability of beam switching in E-plane, and high gain. These advantages makes it a good candidate for the wireless communication systems.

Cu/Co Multilayer-Based High Signal Integrity and Low RF Loss Conductors for 5G/Millimeter Wave Applications

This paper presents copper/cobalt (Cu/Co) multilayer-based low RF loss conductors and their usage in high signal integrity coplanar waveguide (CPW) transmission lines (TLs) and high Q-factor inductors for the applications of millimeter wave bands including a 28-GHz 5G communication band. Low conductor loss, reduced signal dispersion, and low noise figure of the fabricated devices are featured. CPW (TLs) employing 10 pairs of Cu (150 nm)/Co (25 nm) superlattice conductors, the so-called metaconductors, have been designed and fabricated. Their RF characterization has been performed. Experimental results show a broadband RF resistance reduction of up to 50% (max.) in 7–32 GHz (3.5 Octaves), a phase delay improvement of 25.5%, and a thermal noise voltage reduction of 33% compared to reference Cu-based CPW TLs. In comparison with the devices from the other literature, the presented TLs show the best signal integrity performance in Ku, K, and Ka bands. In addition, a high Q-factor planar inductor on a glass substrate has been designed, fabricated, and characterized as an example of high-performance RF passive components, showing record high Q-factors of 54 at 28 GHz and 63.5 (max.) at 29 GHz.