This study investigated the dielectric loss factor and leakage current measured on glass and porcelain insulators at different levels of contamination and humidity. The dielectric loss factor and ...leakage current were measured at an industrial frequency of 50Hz using an independent low THD voltage source to eliminate interference from the power network. The results showed that the dielectric loss factor was only slightly affected by changes in applied high voltage, while the leakage current was highly dependent on changes in applied voltage. Both parameters appeared to be sensitive to changes in relative humidity and contamination levels. These findings have practical implications for the diagnosis and maintenance of high voltage insulators.
•The dielectric loss factor is less voltage-sensitive than leakage current.•The dielectric loss factor could diagnose insulator contamination.•Dielectric loss factor rates contamination severity differently from leakage current.
In this work, an efficient, cost-effective, and less time-consuming citrate precursor wet chemical approach was employed to prepare a series of Calcium (Ca) doped Magnesium–Zinc ferrite of ...composition Mg0.4Zn0.6-xCax Fe2O4 (0.0 ≤ x ≤ 0.6). X-ray diffraction (XRD), Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX) analysis confirmed the spinel structure and nanometric size of the particles. Williamson-Hall (W–H) plots were drawn by making use of XRD data and calculated values of lattice strain were found in the range (3.00 × 10−3 to 9.09 × 10−3) for various concentrations of calcium. The cubic spinel structure of produced ferrites was also verified by three active Raman modes (A1g, Eg, and T2g). In the Vibrating sample magnetometer (VSM) study, an “S” shape curve shows the low values of coercivity for all the samples in the range 59–105 Oe. For all Ca concentrations, the dielectric loss tangent values were evaluated to be extremely low 0.03 to 0.18 at 1 MHz frequency. The highly magnetic nature and very low value of loss factor make this prepared nanoferrite material best suited for the manufacturing of high-frequency application devices.
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•Coercivity values in the range 59 to 105 Oe were noticed.•Three active Raman modes (A1g, Eg, and T2g) were observed.•A significant saturation magnetization 15.47 to 38.54 emu/g was found.•A very low dielectric loss tangent value of 0.03 - 0.18 was found.
The dielectric properties of potatoes in the moisture content range of 8.3%–75.4% (w.b.) and the temperature range of 25 °C–85 °C were measured with a coaxial probe network analyzer. The regression ...equation of loss factor of potatoes with its moisture content and temperature was developed first and then introduced into an established LabVIEW control program to make dielectric loss factor as feedback signal for guiding the power output of the microwave drying system. Results show that the dielectric loss factor of potato chips increased with the increase in moisture content. When the moisture content of potato chips was 35%–75.4%, the loss factor decreased with the increase in temperature. The opposite trend was observed when the moisture content was lower than 35%. The proposed microwave power control scheme based on dielectric loss factor feedback and selected probable procedure on/off ratio can prevent the temperature rise of the material in the middle and last drying stages. This condition ensures the quality of the product.
•Developed the regression equation of loss factor of potatoes with moisture content and temperature.•Established LabVIEW control program to dry potato slices.•Proposed microwave power control scheme based on dielectric loss factor feedback.•Selected on/off ratio procedure was selected to improve product quality.•Control scheme prevented the rise in sample temperature in the middle and last drying stages.
In this article the conventional "solid-state reaction" method was used to synthesize perovskite Li0.4Cd0.6Ba2Ca2Cu3O10+δ. Four main types of compounds were obtained by physically replacing calcium ...oxide with cadmium in proportions 0, 0.03, 0.06 and 0.09, the pure Li0.4Cd0.6Ba2Ca2Cu3O10+δ phase, and the phases Li0.4Cd0.6Ba2Ca1.97Cd0.03Cu3O10+δ and Li0.4Cd0.6Ba2Ca1.94Cd0.06Cu3O10+δ and Li0.4Cd0.6Ba2Ca1.91Cd0.09Cu3O10+δ ,respectively from mixing their constituent oxides and pressed into pelts and then sintered in the furnace at 850 degrees Celsius for 90 hours: These samples have been studied for their original dielectrically properties. The real dielectric constant, dielectric loss factor, and tangent were calculated in the frequency range (50 to 1000000 HZ). It was found that the partial substitution of cadmium oxide plays an important role in enhancing dielectrically properties.
BiScO3-PbTiO3 ceramics are attractive for high-temperature piezoelectric applications while their high dielectric loss has to be substantially reduced. In this paper, a ternary perovskite system of ...xBi(Mn1/2Zr1/2)O3-(1-x-y)BiScO3-yPbTiO3 (abbreviated as xBMZ-BS-yPT) with x = 0.02, 0.04 and y = 0.62–0.67 were fabricated by conventional solid-phase method, and their ceramics were systematically studied with regards to phase structure, microstructure, dielectric and piezoelectric properties. X-ray diffraction results indicate a gradual change from rhombohedral to tetragonal phase with increasing PT composition. Morphotropic phase boundary (MPB) is revealed for the system with x = 0.02, y = 0.64, at which ultralow dielectric loss factor (0.58 %), almost unchanged Curie temperature (449 °C), high electromechanical properties (d33 = 360 pC/N, kp = 0.53), and stable strain output below 200 °C are observed. With such excellent piezoelectric properties and high-temperature stability, BMZ modified BS-PT ceramics are promising candidates for power electromechanical devices, especially operating in high-temperature environments.
The dielectric loss factor is an essential electrical parameter used to evaluate the quality of transformer oil and judge the operation status of transformers. In this work, a new nondestructive ...detection method of dielectric loss factor based on multi-frequency ultrasound technology and artificial neural network is proposed. For the extraction of valid information, dimensionality reduction algorithm Kernel Principle Component Analysis (KPCA) is adopted to pre-process the ultrasound data set before the training of neural network. Particle Swarm Optimization (PSO) and Whale Optimization Algorithm (WOA) are considered for the optimization of Elman neural network (Elman neural network). The analysis of the prediction results shows that the prediction accuracy of WOA-Elman and PSO-Elman are 93.2 % and 85.5 % respectively. Through the comparison of four evaluation indexes, WOA-Elman neural network behaves better on the prediction of the dielectric loss factor. Consequently, the proposal of the prediction model Elman neural network based on Kernel Principle Component Analysis and Whale Optimization Algorithm (KPCA-WOA-Elman neural network) lays a foundation for the effective prediction of the quality of transformer oil online.
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•Based on the attenuation characteristic of ultrasonic wave in medium, the multi-frequency ultrasonic technology is applied to the detection of transformer oil.•The correlation between dielectric loss factor and multi-frequency ultrasonic signal is analyzed.•The dimensionality reduction algorithms KPCA was adopted to pre-process the 242-dimensional data into 36-dimensions and WOA (Whale Optimization Algorithm) was adapted to optimize Elman neural network, with a prediction accuracy of 93.2 %.
Dipole loss of main compositions of powdered infant formula milk (PIFM), including whey protein (WP), fat and lactose and the ionic loss of PIFM were analyzed over frequency range of 10 to 3000 MHz ...at temperature range of 20–80 °C. Dielectric loss factor of PIFM decreased with increasing fat content, while increased with increasing WP content and lactose content at investigated frequencies in our study. The dipole loss of WP, fat and lactose followed Debye equation which increased with increasing frequency till around 1.2,1 and 1 GHz, respectively, and then decreased. Ionic loss of PIFM was constant with increasing frequency at investigated frequencies and increased with increasing temperature. A general formula to calculate ionic loss for both solid and liquid materials was obtained. Validation experiments based on the dielectric loss factor of different compositions indicated that increasing WP proportion in PIFM can increase heating rate in radio frequency field and also result in lower lipid oxidation of treated PIFM. This provides a solution to adjust RF heating performance and product quality based on loss mechanisms of different ingredients.
•Dipole loss of main compositions of PIFM and the ionic loss of PIFM were analyzed.•A general formula to calculate ionic loss for solid & liquid materials was obtained.•Validation experiments were conducted based on loss factor of different compositions.
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•Polypyrrole nanotubes decorated with magnetite nanoparticles are synthesised.•Low-cost electrical devices based on magnetorheological suspensions are designed.•The resistance and the ...quality factor of the newly manufactured electrical devices is addressed.•Electro-magnetodielectric and electro-magnetoconductive effects are induced and are sensibly influenced by the magnetic flux density.•The obtained electrical device can be used for monitoring weak electric and magnetic fields.•The influence of external magnetic and electric fields, and their combinations, to the electrical devices is investigated.
In this work, two magnetorheological suspensions composed of polypyrrole nanorods decorated with magnetite nanoparticles and suspended in silicone oil were studied as electrical devices. The electrical devices (EDs) were fabricated in a unique cell using nanotubes with different magnetic and electric properties which can be tailored during synthesis. The electrical effects of the suspensions were studied under static electric and magnetic fields and were superimposed on a medium-frequency electric field. The electrical resistance Rp and the quality factor Qp at the terminals of EDs were extracted and analysed. Additionally, the equivalent electrical capacitances Cp were obtained through a well-established theory and then compared for each ED. Through the electrical and magnetic dipolar approximation model, it was illustrated that the electrical effect induced in a suspension can be three times higher depending on the amount of the magnetite. Thus, by tuning the synthesis parameters, it is possible to obtain EDs with well-defined and unique properties.
The increased use of vacuum microwave drying in food industry is attributed to shorter drying time and lower temperature. The temperature change of materials is difficult to model due to the vacuum ...condition. A simplified mathematical model is presented subject to some assumptions to predict the temperature distribution in slices made using a mixture of potato and apple purées. Dielectric loss factors of mixed slices were found to increase with temperature and water content. The model accounts for temperature and moisture-dependent dielectric loss factor which yields a useful predictive tool.
