Dissipation Loss Factor Research Articles

Dielectric response of vegetable oil-based nanofluid and impregnated Kraft paper for high voltage transformer insulation

Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied.

Investigations of structural, optical and electrical properties of Zn1-xPbxAl2O4 (0 ≤ x ≤ 2 mol %) ceramic powder

The Pb2+ doped ZnAl2O4 ceramic with different concentrations (0–2 mol %) has been prepared via the fast citrate sol-gel technique. Crystalline size of prepared samples was found in the range of 26–32 nm using XRD data. The X-ray pattern revealed that all samples are polycrystalline in nature with cubic phase and Fd͞3 m space group. The preferred orientation and structure parameter of spinel ZnAl2O4 has been tailored significantly after doping Pb2+ ions. The FTIR technique was used to identify the characteristic functional group of the prepared spinel structure.The optical band gap of Zn1-xPbxAl2O4 (0 ≤ x ≤ 2 mol %) ceramic powder was found to increase from 3.65 eV to 4.36 eV with an increase in Pb2+ content. The prominent emission was observed in the violet-blue region (387 nm) after exciting the sample at 270 nm. The impedance data has been analyzed to explore the dielectric constant (k), dissipation loss factor (DF), and ac conductivity. The observed violet-blue emission and improved dielectric behavior endorse the potential applications of Zn1-xPbxAl2O4 (0 ≤ x ≤ 2 mol %) ceramic powder in UV sensors.

Estimation of Response of Composite Shells to Acoustic Excitation Using Sea and Its Experimental Verification

Shells made up of composite material are extensively used in aerospace structures as they offer excellent specific strength and stiffness properties over their metallic counterparts. These elements experience high frequency and high intensity acoustic loads during the launch. Response behaviour of structures in the high frequency region is analyzed in a Statistical Energy Analysis (SEA) framework. Though the methodology of estimating the response using SEA exists, its applications to composite cylindrical shells and how they compare with experimental results are seldom reported. Present work fills this gap. Acceleration and strain responses of a typical composite sandwich cylinder under diffused acoustic field are estimated in SEA framework. Modal densities and coupling loss factors are estimated using expressions. The dissipation loss factors are determined experimentally. Same cylinder is subjected to diffused acoustic field in reverberation chamber and the accelerations and strains are measured. The work presents how much the theoretically estimated responses compare with the experimentally obtained results. It is seen that the acceleration responses compare reasonably well, but needs improvement. The strain-velocity relations compare very well. Acceleration and strain bounds such that 99 % of all measurements are within are also predicted which could be used in the structural design.

Effect of Iodine-doping toward ZnO critical optical constants and their applications to latent fingerprints detection

The present work focus on the influence of Iodine (I) doping on the improvement of properties of ZnO such as structural, optoelectronic, optical, dielectric and transport. I-doped ZnO materials were synthesized via an easy sol gel method assisted by microwave post-heated treatment. I doping level was 0, 0.025, 0.050, 0.075, and 0.100 at% with respect to Zn content. The deducted physico-chemical properties were based on XRD, Raman spectroscopy, EDS, XPS, SEM imaging, photoluminescence (PL) and UV-Visible diffuse reflectance (UV-Vis DRS) spectroscopy. The prepared nanomaterials were applied to latent fingerprints detection. The determined optical constants were based on diffuse reflectance data and consequently the refractive index and extinction coefficient. Tauc’s equation was used to evaluate both band gaps and inter-band transitions as impacted by doping. The dielectric properties, optical and electrical conductivities dependence on both frequencies and I-doping level were studied. Dissipation loss factors including surface and bulk contributions were evaluated. The dynamics of transport with the consideration of the four components dielectric relaxation time (τ), optical resistivity (ρopt), optical mobility (μopt), and optical charge carriers (Nopt), were discussed in terms of photons energy assessment and materials composition. The optical covalency and optical electronegativity modification were considered. IxZnO nanomaterials were applied successfully to fingerprint detection on various substrates such as glass surfaces, coins, and plastic sheets. Both I0.025ZnO and I0.1ZnO materials were identified as a potential candidate for forensic application.

A framework to predict the airborne noise inside railway vehicles with application to rolling noise

A framework is described for predicting the airborne noise inside railway vehicles which is applied to rolling noise sources. Statistical energy analysis (SEA) is used to predict the interior noise by subdividing the train cabin into several subsystems. The dissipation loss factors are obtained from the measured reverberation time in the train cabin. The power input to the interior SEA model is obtained from the external noise sources by multiplying the incident sound power on the external surfaces with measured transmission coefficients of the train floor and sidewalls. The sound power incident on the train floor is calculated by using an equivalent source model for the wheels and track together with an SEA model of the region below the floor. The incident sound power on the sides is obtained by using a waveguide boundary element (2.5D BE) method. The procedure is applied to a Spanish metro train vehicle running in the open field for which rolling noise is the main external noise source. The procedure is verified by field measurements of sound pressure beneath the carriage, on the sidewalls and inside the vehicle. The sensitivity of the results to changes in interior absorption is also studied, including the effect of passengers.

Moisture resistant stones waste based polymer composites with enhanced dielectric constant and flexural strength

Moisture resistant and high strength industrial stone waste powder based hybrid polymer composites are prepared using simple and cost effective compressive casting technique. Hybrid polymer composites of inorganic stone waste powder are fabricated with various filler concentrations of 10, 20, 30, and 50 wt% in epoxy resin matrix system. Mineral composition of stone waste powder was determined using X-Ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) technique was performed to measure the dimension and surface morphology of stone powder and polymer hybrid composite. The variation of dielectric constant, dissipation factor, ac electrical conductivity of raw stone waste powder and their polymer composite were analyzed for their potential application in electrical insulation and microelectronics. High dielectric constant of 275 at 20 Hz and low dissipation loss factor of 0.02 at 2 MHz were observed for stone waste powder. Dielectric constant of stone based polymer composites was decreased significantly from 275 to 45, 47, 55, and 60 for filler concentrations of 10, 20, 30 and 50% in epoxy matrix, respectively. Ultra low water absorption of 0.08% and high flexural strength up to 39 MPa were achieved with 50 wt % stone. Such low water absorption, high dielectric constant and flexural strength make it suitable for durable and sustainable electrical insulting and advanced construction materials applications though eco-friendly process.

Dielectric properties of kenaf filled epoxy composites

The dielectric properties of kenaf filled epoxy composites was investigated. Composites was fabricated using kenaf fibres and epoxy resin. The composites was manufactured using a cold press method; the volume fraction of the natural fibres were 7 and 14%. The dielectric test were conducted using Agilent/Keysight E8363B PNA Network Analyser. Result shows that the 14% Kenaf filled epoxy composites successfully decrease the dielectric constant between 12.4 GHz and 16.66 GHz. It shows that the dielectric constant increased with decreased on the fibre loading. Besides that, 14% Kenaf has a higher dissipation loss factor compared to 7% Kenaf filled epoxy composites and reached its peak at 17.89 GHz. In summary, the 14% Kenaf shows a lowest dielectric constant and permeability compared to 7% Kenaf filled epoxy composites.

Statistical energy analysis on vibrational energy transmission in hard disk drive components

One of the problems found in the 2.5 in. hard disk drives (HDDs) in operation is the vibration of the HDD case. Aiming to find crucial information to reduce the vibration transmitted to the outer shell of HDD, the parameters involving vibrational energy transmission through the main components of HDD are identified by the test-based statistical energy analysis (SEA). First, the vibration tests of HDD in the idle mode are performed in order to identify the contribution of the main components; the top cover, the platters, and the actuator arm to the overall vibration of HDD. The SEA parameters including the dissipation loss factors of the individual components and coupling loss factors of the pairs of the components are then experimentally determined in order to calculate the vibration transmission power among the components. The determined parameters, hence, provide some vibrational energy transmission characteristics to facilitate the design of the HDD components to generate less vibration. With some further studies using this concept, the vibration due to shock exerted to the shell of HDD that is transmitted to main components inside the HDD can also be reduced.

Statistical energy analysis of non-resonant response of isotropic and orthotropic plates

The conventional SEA model considers only the resonant part of the structural response to an acoustic excitation. Therefore, this study investigates non-resonant responses of isotropic and orthotropic plates to acoustically induced vibrations in a reverberation chamber. A modified SEA model is introduced to predict the non-resonant plate response. The estimated non-resonant and resonant responses are then compared with those obtained experimentally, and good agreement is observed for isotropic and orthotropic plates. For an isotropic plate with a small dissipation loss factor, when the non-resonant part is ignored, the estimated response can lead to significant errors at frequencies near and above the critical frequency, while large errors may occur at frequencies below the critical frequency for an orthotropic plate with a high dissipation loss factor. The experimental study indicates that the non-resonant response component should be included in the estimated responses to enhance predictive accuracy.

Electrical properties of polyimide thin films formed by the vapor deposition polymerization method

Thin films of polyimide (PI) were fabricated by a vapor deposition polymerization method (VDPM) and studied for their insulator characteristics in semiconductor devices. Polyamic acid (PAA) thin films fabricated by vapor deposition polymerization (VDP) from PMDA (pyromellitic dianhydride) and DDE (4,4′-diaminodiphenyl ether) were converted to PI thin films by thermal curing. The appropriate curing temperature was 300 °C. From TG-DTA (Thermo Gravimetry-Differential Thermal Analysis), the PI thin films can endure 230 °C for 20 000 h. They exhibited a relative permittivity of 3.9–3.5 and a dissipation loss factor of 0.008 at frequency of 10 kHz in the temperature range from 25 to 200 °C. The resistivity was approximately 3.2×10 15 Ωcm and the dielectric breakdown strength was 4.61 MV/cm.

An Evaluation Method for the Prediction of the Maximum Remaining Life of Measuring Transformers in 150Kv Power Systems

From measurements of AC dissipation loss factor (tgd), shock wave partial discharges, and DC insulation tests performed on 150 kV distribution network measuring transformers, valuable and accurate information can be given for the insulation condition of the winding dielectric material. In conjuction with the initial dielectric routine and type tests, it is possible to predict the maximum life limit of the transformer. This method is applicable to electrical network equipment bearing any kind of dielectric material (mainly to transmission and distribution transformers).

Pulsed laser deposition and ferroelectric properties of SrBi 2Ta 2O 9 thin films

Ferroelectric SrBi 2Ta 2O 9 (SBTO) thin films were successfully produced on Nb-doped SrTiO 3 and Pt-coated SrTiO 3 substrates by pulsed laser ablation of SrBi 2.5Ta 2O 9 ceramic targets (25 mol% bismuth excess) and a KrF excimer laser. Very weak spontaneous polarization was observed for c-axis-oriented SBTO thin films on Nb-doped SrTiO 3 substrates. For films deposited at 705°C on Pt/Ti/STO (100) substrates, the small signal dielectric constant and dissipation loss factor at 1 kHz were 370 and 0.020, the remnant polarization and coercive field were 4.2 μC/cm 2 and 30 kV/cm at 9 V and 1 kHz, and the decay of remnant polarization at a fatigue measurement was less than 6% up to 10 10 cycles. The effects of film microstructure on the degradation of spontaneous polarization are also discussed.

A TECHNIQUE FOR THE ASSESSMENT OF STRENGTH OF COUPLING BETWEEN SEA SUBSYSTEMS: EXPERIMENTS WITH TWO COUPLED PLATES AND TWO COUPLED ROOMS

In a previous paper a technique for the indication of strength of coupling between SEA subsystems was proposed on the basis of theoretical models. This paper presents the results of an experimental application of the technique to two plates coupled by a variable number of straps and to two rooms coupled by an aperture. Similar values of the coupling strength indicatorCsto those theoretically evaluated are observed. Although not strictly comparable, the indication of dependence of coupling “strength” on coupling configuration and frequency, based upon the ratio of coupling to dissipation loss factors, support the credibility ofCsas a means of signalling unsatisfactory selection of SEA subsystems for experimental purposes.

ENSEMBLE AVERAGED VIBRATION ENERGY FLOWS IN A THREE-ELEMENT STRUCTURE

Closed form expressions are presented for ensemble averaged vibration energies and energy flows in a three-element structure. The ensemble consist of one-dimensional elements, having random lengths with an uncertainty that is plus or minus a quarter of the wavelength. The ensemble averages are functions of only the ensemble averaged input power, the modal densities, the dissipation loss factors and the transmission factors for the couplings, found from travelling wave analysis. The ensemble averages are not related to each other according to the SEA hypothesis that energy flow is proportional to the difference of coupled elements' modal energies. However, energy balance is governed by terms directly proportional to differences of modal energies while also relating non-directly coupled elements. Numerical investigations of this indirect energy flow indicate a measure of coupling strength: i.e., the ratio of the transmission factor to the product of the two modal overlaps in both connected elements. Based on the proposed measure, series expansions are made showing that when coupling is weak and when the response in each element is reverberant, the SEA hypothesis is true. Also, the ensemble averaged energies are then determined by a standard SEA model by using travelling wave estimates of the coupling loss factors.

Use of Statistical Energy Analysis for Rotating Machinery, Part I: Determination of Dissipation and Coupling Loss Factors Using Energy Ratios

A method for determining the dissipation and coupling loss factors of a fully assembled machinery structure is presented in this paper. The method is based on the experimental measurements of the total loss factors and the energy ratios between the subsystems of the machine structure when fully assembled. The presented approach, which will be referred to as the energy ratio method, is suitable for both conservative (no energy dissipation at the junction) and non-conservative coupling. Not only does this energy ratio method determine the coupling loss factors for directly coupled subsystems, but it also determines the coupling loss factors between subsystems which are not directly coupled. This type of coupling exists when the subsystems of the structure are small compared to the wavelength of vibration and all coupling interfaces are in the near field of each other. A series of experiments are carried out to demonstrate the use of this approach and to verify the accuracy of this method for predicting the energy distribution among a set of coupled subsystems. The determined coupling and dissipation loss factors are used in a Statistical Energy Analysis (SEA) model of a rotating machinery component and the estimated results for the response are compared to the directly measured results. As expected, the agreement between the SEA estimated results and the directly measured results is good.

On the measurement of the coupling loss factor of structural connections

Previous attempts to measure the coupling loss factor of structural joints have shown that the results are very sensitive to small errors in the measurements. As the energy transfer at the joints is usually smaller than the dissipation loss in a structural member. the direct measurement of the coupling loss factor is very difficult. In this paper a development of the in situ measurement method used by Bies and Hamid is described. An iteration technique is used to give estimates of the coupling loss factor and individual dissipation loss factors which provide the best fit to the experimental data. Results for a simple two plate configuration compare well with theory for the coupling loss and independent measurements for the dissipation loss factors. The method is then applied to the junction of a plate and cylinder where the coupling loss is somewhat lower than that of the two plate junction.

Experimental Determination of Vibration Parameters Required in the Statistical Energy Analysis Method

In the high frequency range of vibration the Statistical Energy Method provides one of the most convenient ways of estimating vibration levels in structural components. The dynamic characteristics of the structure are described in terms of the modal densities, dissipation loss factors and coupling loss factors of the component parts. Theoretical and semiempirical results are available for some typical components. This paper describes the development of indirect methods for the experimental determination of these three parameters. Where theoretical results are available the experimental results show reasonable agreement. The results of tests on a range of components are described.