Loss Angle Tangent Research Articles

The molecular mobility of the epoxy binder in a modified composites by electric-hammer

In this work, the study of molecular mobility in the surface layers by the method of determining the dielectric characteristics of materials modified by electrospark hydraulic shock, determined the optimal content of the dispersed filler. Comparative data of the tangent of the dielectric loss angle of treated and untreated composite materials are presented.

К вопросу создания усовершенствованных огнестойких кабелей среднего напряжения и методов их испытаний

The article addresses problems faced in designing medium voltage fire resistant power cables. These cables must operate reliably during 30–40 years under the influence of relatively strong electric field, long-term heating up to 90 оC, and short-term heating up to 130 оC. These cables must also retain serviceability for a limited period of time when subjected to a flame source with a temperature of (830±40) оC. The article presents the key state-of-the-art electrical characteristics of these cables (dielectric strength, dielectric loss angle tangent in the delivery state, etc.), the thermal ageing resistance test procedure, the results of studies of long-term electrical strength (life curves) of fire-resistant cable models, and the fire resistance proper of results test. The article also proposes a mathematical model of the processes that take place in performing fire-resistance tests of medium voltage cables. The obtained modeling results are in qualitative agreement with the experimental data.

In Ukrainian

Development of methods for controlling the change in the functional cover and the energy composition of the surface of detonation synthesis diamond nanopowders is necessary to create stable suspensions and materials from them. The aim of this work is to study changes in the electrokinetic and electrophysical characteristics of the powder as a result of the modification of detonation synthesis diamond nanopowders using a liquid-phase thermochemical treatment. Diamond nanopowders of grades ASUD-75 - ASUD-99 with different sp2-hybridization carbon content, manufactured at the V.I. Bakul National Academy of Sciences of Ukraine from the product of detonation synthesis of diamond from the company "ALIT" (Zhytomyr) investigated. Diamond nanopowders of ASUD-90 grade after their modification by means of liquid-phase thermochemical treatment using: a melt of alkalis, a mixture of nitric and sulfuric acids, a mixture of chromic and sulfuric acids were investigated by electrophoresis using a device "Dzeta-potential-analizer" company "Mikromeritiks". Electrokinetic characteristics of diamond nanopowders: the magnitude and sign of the electrokinetic potential, electrophoretic mobility are determined. The methods were used to study the physicochemical characteristics of nanopowders: electrical resistivity, carbon content of sp2-hybridization, mass fraction of impurities in the form of an incombustible residue, and specific surface area. In this work, it was established by electrophoresis that the value of the electrokinetic potential and electrophoretic mobility of the powder decrease by 2-10 times with a decrease in the mass fraction of sp2-hybridization carbon from 23.6 to 0 wt%. Using the ASUD-90 nanopowder as an example, it is shown that the modification of the nanopowder by the liquid-phase method using thermochemical treatment with mixtures of oxidants leads to a decrease in the values ​​of electrophoretic mobility by 1.1-7.5 times and electrokinetic potential by 1.1-7.3 times. It was found by dielectric measurement that the tangent of the dielectric loss angle of diamond nanopowders of grades ASUD-90 - ASUD-99 is in the range 0.3046 - 0.3146. Modification of the ASUD-90 grade nanopowder using a liquid-phase thermochemical treatment leads to a change in the interval of the dielectric loss tangent, namely 0.2450-0.3249. According to the degree of increase in the ratio of the dielectric loss tangent from 0% humidity to 100% humidity, the methods for modifying nanopowders can be arranged as follows: modifying using a melt of alkalis (ASUD-90-1 sample, S = 12.8%) <mixture of chromic and sulfuric acids (sample ASUD-90-3, S = 13.8%) <mixture of nitric and sulfuric acids (sample ASUD-90-2, S = 20.8 %).

The estimation of ship cable condition by the means of measuring its insulation characteristics

Timely detection of defects in electrical equipment and cable network is required for the ensuring the fire safety of a modern marine vessel. The method of continuous monitoring of the resistance value of cable insulation is not very informative and is not applicable for assessing the service life of cables and predicting their replacement during operation and repair. Currently the problem of developing modern non-destructive methods of insulation control is very urgent in order to determine the operability of the cable, search for diagnostic parameters characterizing the state of insulation during prolonged aging, as well as the introduction of traditional methods of diagnostics of electrical equipment that have shown their effectiveness at the facilities of the coastal infrastructure. A promising solution for this problem is a method for monitoring the values of the tangent of the dielectric loss angle tgδ of cable insulation using devices that allow registering parameters with high accuracy. In this study the determination of changes in the parameters of a ship cable subjected to accelerated thermal aging at temperatures 120-130 °C has been made. The tgδ measurements of the cable sheath have been carried out using the Tangent-2000 insulation meter. The tests have shown that aging of cable hose insulation is accompanied by a non-linear change in tgδ; at certain values of the tangent of dielectric loss angle, visible cracks appear indicating the onset of an emergency condition of the cable. The nature of the change in the parameter tgδ is explained by the occurrence of reactions of oxidative dehydrochlorination of polychloroprene in the process of thermal aging of insulation and changes in its mass. Thus, the tangent of the dielectric loss angle can be one of the diagnostic parameters for assessing the state of the insulation of the ship's cable and predicting its service life.

Mathematical Model of a High-Frequency Hygrometer for Cotton Seeds Based on Substitution Circuits

This is a review of high-frequency methods for measuring and controlling the humidity of various materials. The moisture of cotton seeds is a major factor affecting their qualitative and quantitative characteristics in technologies for their storage, transport, and processing. Thus, direct humidity measurements of cotton seeds during processing is an important problem. A mathematical model of a high-frequency hygrometer for cotton seeds is constructed in which the test material is represented as a complicated dielectric in an electric field. A substitution circuit containing a capacitance between electrodes is proposed, along with capacitances and resistances corresponding to different forms of polarization. Four variants of the substitution circuit are examined which approximately describe the dependence of the tangent of the dielectric loss angle on the frequency of the electromagnetic field. It is shown that the simplest parallel two-component RC substitution circuit corresponds most closely to the actual object of measurement at frequencies of 105–108 Hz.

Influence of composition nonstoichiometry and ordering effects on the properties of ferroelectric ceramics based on lead magnoniobate

The effects of violation of the stoichiometry of lead magnoniobate in the preparation of compositions (1-x)PbMg1/3Nb2/3O3 – xPbMg1/2Nb1/2O2,75 with a step of 0.1 and 0≤x≤1 have been studied by X-ray diffraction methods. Differences in the unit cell parameters of the ferroelectric ceramic samples of the composition under study were found. It was shown that the effect of ordering of different types of atoms in the cells, leading to the formation of a superstructure and a doubling of the lattice period, was not observed in any of the samples. . Measurements of the dielectric constant of the synthesized samples and the tangent of the dielectric loss angle showed a violation of the Curie-Weiss law, which indicates the diffusion of the phase transition.

Electrical properties of "water in castor oil" emulsion

The results of the research into the electrical properties of the in castor emulsion, which make it possible to substantiate the technology of castor oil purification from plant impurities and water in an electric field, were presented. The experimental studies of the electrical properties of the in castor emulsion revealed the dependences of specific resistance to direct and alternating currents and dielectric loss angle tangent on the temperature and water content. It was proved that the active component of specific resistance to the suspension in castor on AC is smaller than resistance to DC. That is why, at the temperature of 80 °C and water content of 2 %, heat release on AC is 10 % higher than the heat release on DC. According to this, it is advisable to perform the process of castor oil purification from plant impurities and water residues on AC. This makes it possible to obtain additional heat release and thereby compensate for heat losses for the vaporization of flotation bubbles, which leads to the stable process of flotation purification. A comparison of the magnitudes of polarization losses and losses of end-to-end electrical conductivity for pure oil indicates their identical order. The addition of water leads to an increase in polarization losses due to the structural and dipole polarization of water as a polar fluid. Due to this, from the theoretical point of view, it can be argued about additional local heat release on finely dispersed water drops in the quantity, which can ensure the compensation for the heat needed for vaporization. According to this, vaporization does not require indirect heating of the electrode area from an external source at the expense of thermal conductivity. The obtained results of the experimental research make it possible to substantiate the technological and structural parameters of the electro-technological complex of castor oil purification in the electric field of the cylindrical system of electrodes

Influence of κ-Carrageenan, Modified Starch and Inulin Addition on Rheological and Sensory Properties of Non-fat and Non-added Sugar Dairy Dessert

<P>Background: The high amounts of fat, sugar and calorie existing in dairy desserts can lead to increase the risk of health problems. Therefore, the development of functional and dietary forms of these products can help the consumer health. </P><P> Objective: This study aims to investigate the effects of κ-carrageenan, modified starch and inulin addition on rheological and sensory properties of non-fat and non-added sugar dairy dessert. </P><P> Methods: In order to determine the viscoelastic behavior of samples, oscillatory test was carried out and the values of storage modulus (G′), loss modulus (G″), loss angle tangent (tan δ) and complex viscosity (η*) were measured. TPA test was used for analysis of the desserts’ texture and textural parameters of samples containing different concentrations of carrageenan, starch and inulin were calculated. </P><P> Results: All treatments showed a viscoelastic gel structure with the storage modulus higher than the loss modulus values. Increasing amounts of κ-carrageenan and modified starch caused an increase in G′ and G″ as well as η* and a decrease in tan δ. Also, firmness and cohesiveness were enhanced. The trained panelists gave the highest score to the treatment with 0.1% κ-carrageenan, 2.5% starch and 5.5% inulin (sucralose as constant = 0.25%) and this sample was the best treatment with desirable attributes for the production of non-fat and non-added sugar dairy dessert. </P><P> Conclusion: It can be concluded that the concentration of κ-carrageenan and starch strongly influenced the rheological and textural properties of dairy desserts, whereas the inulin content had little effect on these attributes.</P>

Influence of the organoclay localization on structure features and properties of polyamide 6/functionalized polyolefins blends

The effect of 1.5 wt. % Cloisite 30B organoclay (Cl30B) containing the hydroxyethyl fragments in the surfactant structure on polyamide 6 (PA 6) / functionalized polyolefin (fPO) – a mixture of linear low-density polyethylene and ethylene copolymer with higher olefin – on the structure, mechanical and rheological properties of the materials was studied. The fPO concentration in the blends was varied from 15 to 50 wt. %. The fPO production and the blend compounding were carried out in melt using a twin-screw mixing reactor. The organoclay in the composition of the blends was introduced in two ways: simultaneously with all polymer components (one-step process) and with its preliminary localization in the PA 6 phase (two-step process). It was established that the complex of static and dynamic mechanical and also rheological characteristics of materials and the crystallisability of the components in the blends depend on the way of the Cl30B distribution in the PA6 and fPO phases, as well as on the phase structure of the blends. The organoclay localization mainly in the polyamide phase leads to a 1.3–3.0 time increase of the impact strength of the blends in which fPO forms a dispersed phase and increases their deformation capacity under tension up to 1.2 times regardless of the phase structure. The organoclay blends localized in the PA 6 phase have increased the values of melt flowability and mechanical loss angle tangent at the PA 6 a-relaxation transition and dynamic shear modulus in the temperature range from –100 to 150 °С compared to the materials produced by one-stage technology, which is explained by the blocking of organoclay amide and other polar groups in the structure of PA6 macromolecules in the polyamide phase and by a decrease as a result of this intensity of interfacial interactions with fPO.

The Initial Requirements for the Heat Exchanger for Gathering Phase Transition Energy

Production of heat power equipment and provision of agricultural production facilities with it is less than 40 percent, so it is important to conduct research on the development of domestic heat exchange equipment. (Research purpose) The research purpose is in developing the initial requirements for the heat exchanger of an experimental installation in order to gather the energy of the water-ice phase transition for its manufacture. (Materials and methods) Authors conduct patent search on the websites of the World Intellectual Property Organization, Rospatent, Google patents, the European Patent Office and the Eurasian Patent Organization. The article presents drawings using the COMPASS-3D V17 graphic editor. (Results and discussion) The article presents an energy-saving system for maintaining the microclimate of an agricultural facility using a heat pump. It was found that the thermal and physical parameters of the coolant (freezing point, thermal conductivity, solubility of salt, density) as water and salt solutions of various concentrations, as well as electrical and physical parameters (permittivity, tangent of the dielectric loss angle, electrical conductivity, temperature coefficient of electrical conductivity) change during external electrophysical treatment (exposure to an electric field, including electric freezing), magnetic field (including alternating magnetic field in the ultrahigh frequency range, low-frequency magnetic field, weak infra-low frequency magnetic field). (Conclusions) The energy-saving, eco-friendly heat exchange equipment with a heat pump unit is designed to maintain the microclimate of agricultural facilities. The article presents the initial requirements for the heat exchanger of the experimental installation for obtaining the energy of the water-ice phase transition, which will allow producing an experimental sample. Authors have developed a scheme for a heat exchanger of an experimental sample of heat exchange equipment with a heat pump unit for gathering energy of the water-ice phase transition.

Study on Dielectric Material for Generating Ozone by Dielectric Barrier Discharge

Dielectric barrier discharge is mainly used to produce ozone in industry. The dielectric plays an important role in this form of discharge. Because of their good physical and chemical properties, some kinds of ceramic material and enamel material have been studied and applied as the dielectric. Experiments show that as frequency increases, dielectric constant and loss anlge tangent of all ceramic samples decrease. For samples with larger dielectric constant, dielectric constant decreases faster, and the magnitude of the decrease is larger. When the frequency is high, dielectric constant and the loss angle tangent basically stabilize. At the same frequency, the loss angle tangent of ceramic samples with high dielectric constant is also higher. The dielectric constant and loss angle tangent of different ceramic samples differ greatly at low frequency, while the difference is relatively reduced at high frequency. From the perspective of electrical performance, ceramic dielectrics are not much superior to enamel dielectrics. Enamel material is more advantageous than ceramic material.

Диэлектрические характеристики эпоксидной смолы, модифицированной тетраэтоксисиланом, в миллиметровом диапазоне

In this work, the influence of alkoxysilanes introduced into the epoxy resin was studied. That was done in order to study the possibility of using the obtained binders in composite materials with increased radio transparency in the millimetre microwave radio band. Determination of the modified epoxy resin dielectric characteristics in the millimetre microwave radio transparency was carried out by the waveguide method. The measuring complex consisted of a precision measuring line P1-31, a tunable generator on a Gann diode (30-38 GHz), a ferrite gate, and a section of a standard-section waveguide. Based on measurements of the minimum position displacement of the standing wave coefficient by known propagation constants, the free-space wavelength λ0 for a given operating frequency, and the critical wavelength in the waveguide λcr, the loss angle tangent tg(δ) and the permittivity ε were calculated. Calculations of the permittivity ε, the angle of the dielectric loss tg(δ) and the radio transparency loss-ΔР were performed in the MathСad. Moisture absorption of samples was determined by holding them in a desiccator with a humidity of 98 %. The samples were kept in a tightly closed desiccator for 24 hours at a temperature of 25 oC. In addition, the relative moisture absorption was determined using the increase in mass. It was found that the introduction of tetraethoxysilane in the composition in an amount of 1.5-3.5% leads to a decrease in the tangent of the dielectric loss angle. The optimum is observed in the range of the modifier concentration of 2.5-3.5%. This fact confirms that at these concentrations there is a complete interaction of TEOS alkoxygroups with epoxy resin epoxygroups.

A METHOD OF WAVELET ANALYSIS OF TIME SERIES OF PARAMETERS OF DIELECTRIC ABSORPTION OF ELECTRICAL INSULATING STRUCTURES

Introduction: In the objects of control there are always a number of interfaces, for example, solid insulation – electrode. On contacting surfaces, free surface charges are transferred. Surface conductivity leads to fluctuations in the measured values of the capacitance and the tangent of the dielectric loss angle of solid insulation, the state of which is determined. The drain off of the surface charge does not lead to a decrease in the scatter of the measured dielectric absorption parameters. One of the main reasons for the significant time spread of the dielectric absorption parameters, and to a large extent (three orders of magnitude) of the dielectric loss tangent are tribo charges caused by triboelectrification of cable structural elements. Tribo charges cause internal noise in electrical insulating structures, masking processes in the polymer insulation itself. Purpose: Substantiation of a method for analyzing the time series of dielectric absorption parameters, which provides increased accuracy of control and diagnostics of solid polymer insulation of electrical insulation structures based on filtering experimental data using wavelet transform. Methodology: The inefficiency of filtering the spectra of time series using a low filter based on the direct Fourier transform is shown. Multilevel wavelet decomposition of the time series of parameters is presented, and the efficiency of applying wavelet transforms to identify high-frequency and low-frequency components in the measured values. Practical value: The method of analyzing the time series of dielectric absorption parameters using the wavelet transform, proposed for the first time, makes it possible to increase the accuracy of monitoring and diagnostics of solid polymer insulation both at the manufacturing stage and in the operation of electrical insulating structures. This method is the basis for creating a database of control results for assessing the state of solid polymer insulation of electrical insulation structures, in particular, power and information cables.

Low-temperature phase transition in bismuth ferrite films substituted by manganese

Measurements of the capacitance and tangent of dielectric loss angle, impedance and resistance, magnetization in a magnetic field of 8.6 kOe BiMnxFe1-xO3 films in the temperature range 80-600 K were carried out. The anomalies of the dielectric properties are explained in the Debye model and correlate with changes in the magnetic moment versus temperature.

Effect of Nano-MgO Particles Doping on Breakdown Characteristics of Polypropylene

In this article, the nano-MgO particles were used as inorganic fillers, and polypropylene (PP) polymer was used as a matrix. The nano-MgO/PP composites were prepared by double melt blending. Using the polarization microscope (PLM) test and hot-stage microscope test, the crystalline morphology of PP and nano-MgO/PP with different mass fraction were observed. Using the differential scanning calorimetry (DSC) test, the parameters and crystallinity in the process of isothermal crystallization could be obtained. Additionally, the samples of pure PP and nano-MgO/PP composites were dealt with using a breakdown test and a dielectric frequency spectra test. From the experimental results, nano-MgO particle doping decreased the samples’ crystal size, and the crystalline structure was converted from large spherulites to fascicled crystallization. Additionally, the crystallization rate became fast and crystallinity increased. According to the breakdown test, the nano-MgO particle doping made the composites form small, dense spherulites. The breakdown developed through a longer path, so the composites’ breakdown strength rose greatly. When the mass fraction of nano-MgO particles was 3%, the shape parameter of the composites’ Weibull distribution β was larger, which illustrated that the nano-MgO particles were dispersed uniformly in the PP matrix. According to the dielectric frequency spectra test, the dielectric constant of different nanocomposites were all lower than which of pure PP, but the loss angle tangent values were all higher than which of pure PP.

Research on Electromagnetic Sensitivity Properties of Sodium Chloride during Microwave Heating

AbstractThe multimode resonant cavity is the most common cavity. The material often shows on selective heating performance during the heating process due to the effect of microwave heating having a closely relationship with the electromagnetism parameters. This paper is based on finite difference time domain method (FDTD) to establish the electromagnetic-thermal model. The electromagnetic sensitivity property parameters of sodium chloride including relative dielectric constant, loss angle tangent and water content of sodium chloride is studied during the heating and drying process. The heating rate and the electric field distribution of sodium chloride, at the different water content, were simulated with the electromagnetic characteristic parameters changing. The results show that with the electromagnetic sensitivity property parameters varying, the electric field strength, heating rate and steady-state temperature of the heating material will all have a variety in the cavity. Some measures are proposed to improve the heating efficiency and ensure the stability of the microwave heating system in the industrial application.

Preparation and study of Ce2Fe17N3 microflakes with easy-plane anisotropy and high working frequencies

Soft magnetic composites (SMCs) are effective as magnetic powder cores in power transformers. Currently, SMCs used in transformers are mostly prepared from NiZn ferrites. One example of this type of material is NiZnCu ferrite, whose working frequency limit is 40 MHz. Above this frequency, its large magnetic loss angle tangent ( tanδm), approximately equal to 0.29 at 100 MHz, seriously impairs the property of transformers. Generally, the magnetic losses in the MHz frequency band result from eddy-current loss, domain wall resonance, and natural resonance, specifically the high natural resonance loss. A way to decrease it is by increasing the resonance frequency (fr). However, the increase in fr is very difficult for the uniaxially anisotropic NiZnCu ferrite due to the Snoek limit. We present a composite of oriented Ce2Fe17N3 microflakes and polyurethane in this letter. Although its true permeability is not as high as that of NiZnCu, the fr reaches 7.5 GHz. As a result, the tanδm at 100 MHz is decreased to 0.015. This indicates that our material has a higher working frequency than NiZnCu and should make fabrication of a 100 MHz transformer possible.

ERROR OF CONTROL OF ELECTRICAL INSULATION STRUCTURES BY DIELECTRIC ABSORPTION PARAMETERS ACCORDING TO THE CONCEPT OF UNCERTAINTY OF MEASUREMENTS

Introduction. Measurements on alternating current of dielectric absorption parameters – capacitance and dielectric loss tangent tgδ allow us to evaluate the quality of insulation of cables, electrical machines, transformers, etc., both at the technological stage of manufacture and in operation. An increase in the reliability of the measurement result of the parameters is provided by a decrease in the measurement error due to the improvement of measuring instruments and measurement methods and an increase in the number of measurements Purpose. The estimation of the error of control of electrical insulation structures by dielectric absorption parameters in accordance with the concept of measurement uncertainty. Methodology. The error of measurements of the capacitance and the tangent of the dielectric loss angle is estimated using the example of a twisted unshielded pair of category 5e. A statistical analysis of the results of multiple measurements of the capacitance and the tangent of the dielectric loss angle of an unshielded cable is carried out. The linear regression equations for the measured values of the dielectric absorption parameters of the number of measurements are obtained. Practical value. Ensuring unity in the methods for estimating the error of measurement results, both when using the traditional concept of «measurement result error» and when introducing the concept of «measurement result uncertainty» into practice, it will allow to unambiguously interpret and correctly compare the results of measurements of the capacitance and tangent of the dielectric loss angle of electrical insulation structures.

Fabrication, structural and dielectric property of lead-free perovskite silver niobate ceramics

Dielectric capacitors with high recoverable energy density are in high demand for their application in electrical and electronic systems. Among lead-free dielectric materials, silver niobate (AgNbO3) has attracted growing interest due to its superior energy storage density at room temperature. The field-induced phase transition from antiferroelectric (AFE) phase to ferroelectric (FE) phase contributes to its large energy density. In this work, pure perovskite silver niobate ceramics were fabricated in an oxygen atmosphere by the solid-state reaction technique. The Pbcm orthorhombic phase of AgNbO3 was closely observed using the Rietveld refinement method to provide explanation for the origin of high spontaneous polarization within a unit cell. Local structural analysis via piezoelectric force microscopy revealed the existence of ferroelectric nano domains, which may contribute to the high energy storage efficiency (η = 99.9926%) in AgNbO3 at low electric fields. The phase transitions of AgNbO3 were also investigated via the dependence of the dielectric permittivity (ε′ and ε″) and loss angle tangent (tanδ) on temperatures, providing insights into the further modification of AgNbO3.

ЧАСТОТНО-ТЕМПЕРАТУРНІ ВИМІРЮВАННЯ ДИНАМІЧНОГО МОДУЛЯ ПРУЖНОСТІ КОНСТРУКЦІЙНОГО ПОЛІВІНІЛХЛОРИДУ

Резонансним методом зсувних коливань вільного кінця закріпленого зразка на звукових частотах у широкому діапазоні температур проведено вимірювання дійсної частини динамічного модуля пружності та тангенса кута механічних втрат конструкційного полівінілхлориду. Показано, що для амплітуд резонансних максимумів послідовних мод коливань зразків існує лінійна залежність.