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Liquid dielectric

About: Liquid dielectric is a research topic. Over the lifetime, 3702 publications have been published within this topic receiving 45150 citations.


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Journal ArticleDOI
30 Jan 2013-Langmuir
TL;DR: The structure of the electric double layer (EDL) is analyzed in order to understand the electromechanical behavior of the interface of ionic liquid-dielectric liquid and it is shown that all the results might be consistent if the leaking of the dielectric layer and/or the adsorption of ions is considered.
Abstract: The structure of the electric double layer (EDL) is analyzed in order to understand the electromechanical behavior of the interface of ionic liquid-dielectric liquid. The modified Poisson–Boltzmann equation proposed by Bazant et al. is solved to see the crowding and the overscreening effects that are the characteristics of an ionic liquid (Bazant, M. Z.; Storey, B. D.; Kornyshev, A. A. Double layer in ionic liquids: Overscreening versus crowding. Phys. Rev. Lett.2011, 106, 046102.). From the simple one-dimensional (1-D) analysis, it is found that the changes of the composition and the material properties in the EDL are negligible except under some extreme conditions such as strong electric field overO(108) V/m. From the electromechanical view points, an ionic liquid behaves like a pure conductor at the interface with a dielectric liquid. Based on these findings, three specific application problems are considered. In the first, a new method is suggested for measuring the interfacial tension of an ionic liq...

21 citations

Journal ArticleDOI
TL;DR: In this paper, a simulation of DEDM single discharges and its numerical interpretation by emission spectra simulation is presented, showing that the discharges are similar to anode dominated vacuum arcs, which present properties very different from EDM discharges.
Abstract: Dry electrical discharge machining (DEDM) has been developed as an alternative manufacturing process to the traditional EDM in liquid dielectric media. The absence of the liquid dielectric allows DEDM to be performed by simpler and environmentally friendlier machines. The erosion in DEDM mainly occurs due to the bombardment of the workpiece electrode surface by charged particles produced by micro electric discharges. Thus, the understanding of the fundamental properties of the micro plasma is necessary to explain the erosion mechanisms in this process. Optical emission spectroscopy of DEDM single discharges and its numerical interpretation by emission spectra simulation are developed in the present work. The hypothesis of plasmas in local thermal equilibrium (LTE) is developed, whereas the formation of an electron beam in non-LTE plasmas is also considered and briefly introduced. The simulations show that large amount of different ionic species is produced from the anode workpiece material, and the estimated electron temperature profile is peaking at the plasma centre. Moreover, hot anode spots formed on the workpiece surface due to the plasma-material interactions seem to be considerably smaller than the total plasma diameter and the respective eroded crater. These characteristics indicate that DEDM produces discharges similar to anode dominated vacuum arcs, which present properties very different from EDM discharges in liquid dielectric.

21 citations

Journal ArticleDOI
TL;DR: A novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl, which has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation.
Abstract: An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(108μW)/(mm2HzV2) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the impact of humidity on the dielectric response of different insulation technologies used for stator insulation of large rotating machines was investigated using time and frequency domain measurements.
Abstract: The study of dielectric response is a significant method to characterize the electrical properties of insulating materials and a useful tool for condition assessment of the insulation systems of rotating machines. Time and frequency domain measurements can be used to determine the dielectric response. Polarization and depolarization current measurements are usually used as a time domain measurement while in frequency domain the capacitance and dissipation factor of the samples can be measured over a broad range of frequencies. The dielectric response of machine insulation is affected by variety of parameters such as degree of aging, contamination and the environmental conditions such as temperature and humidity. In this work, time and frequency methods are used to determine the impact of humidity on the dielectric response of different insulation technologies used for stator insulation of large rotating machines. The measurements were conducted on bars and coils in laboratory conditions as a comparison base and then the dielectric response of the samples was monitored in an environmental chamber during two different humidification periods. The samples were selected to cover the most common materials and technologies used in operating rotating machines including asphalt; epoxy and polyester based insulating systems. The results showed considerable change in the dielectric response when the samples were exposed to moisture. Further studies demonstrated that the change in dielectric response is mostly attributable to the end-winding and stress-grading layer.

21 citations

Proceedings ArticleDOI
01 Aug 2005
TL;DR: In this article, the experimental characterization of discharges propagating on solid/liquid interfaces under impulse voltages using a point-plane electrode arrangement is presented, and it is shown that the nature and the thickness of the solid insulating significantly influence the characteristics of creepage discharge and especially the density of branches.
Abstract: This paper deals with the experimental characterization of discharges propagating on solid/liquid interfaces under impulse voltages using a point-plane electrode arrangement. It's shown that the nature and the thickness of the solid insulating significantly influence the characteristics of creepage discharge and especially the density of branches. This later decreases when the thickness of the solid insulator increases. This indicates the important role of the capacitive effect in the propagation mechanism. For a given thickness, the final length of these discharges increases quasi-linearly with the voltage. The current waveform of creepage discharges depends on the polarity of the voltage.

21 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202328
202267
202191
2020122
2019142
2018120