Liquid dielectric

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

Impact of air bubbles in a dielectric liquid when subjected to high field strengths

Abstract: The dielectric breakdown of gas bubbles entrapped in liquid food flowing through the cavity of a pulsed electric field treatment chamber has been a limiting factor in this non-thermal food preservation technology. Prediction of electric field enhancement due to gas bubbles is an important tool in the design, modification, and optimization of the treatment chamber's electrode geometry and pressurization. Simulation of the electrostatic characteristics of a coaxial treatment chamber with specified voltage of 25 kV, filled with dielectric material with conductivity of 0.6 S/m containing gas bubbles, evidenced a significant perturbation in the electric field. The magnitude of electric fields generated inside the bubbles was almost two times higher than in the homogeneous food. Without pressurization (atmospheric conditions), the dielectric breakdown strength of the gas-filled bubbles was exceeded, thus indicating the risk of arcing. A system pressurization of approximately 8 atm could be sufficient to limit arcing when small gas bubbles (∼1 mm) are present. The presence of gas bubbles caused the field magnitude to decrease significantly near the boundary of the bubble, thus threatening the uniformity of the PEF treatment across the chamber gap. This perturbation in the electric field was more significant when more than one bubble was present or when smaller gaps were used. The dielectric breakdown threshold at a given pressure is more likely to be exceeded by bigger bubbles (>1 mm) entrapped in a fluid processed in smaller treatment chamber gaps (3 mm), than by smaller bubbles (

Dielectric liquid microlens with well-shaped electrode.

Abstract: A dielectric liquid microlens with a well-shaped electrode is demonstrated. The bottom well-shaped electrode and the top planar electrode induce an inhomogeneous electric field when a voltage is applied, which causes the focal length to change. Adaptive microlenses and microlens arrays with well-shaped electrode are fabricated and their performance is evaluated. The bi-convex structure introduces a larger optical power. Compared with common planar-electrodes liquid lenses, this well-shaped electrode not only inhibits drifting of the liquid but also reduces the operating voltage.

Electrical Characterization of a Corona Discharge for Surface Treatment

Abstract: Electrical characterization is based on a display of voltage and charge which appears as a simple parallelogram. The area is a measure of energy input per cycle and is independent of voltage waveform but very dependent on the maximum voltage. A useful model for such corona discharges employs a Zener diode to simulate the corona drop. The buffer dielectric plays a major roll in controlling the corona power, and the air gap importance depends on the electrode system employed. Proper interpretation of the voltage-charge traces provides insight as to the corona performance and serves as a diagnostic procedure for obtaining optimum performance.

Properties of ester liquid midel 7131 as an alternative liquid to mineral oil for transformers

Abstract: The combination of a solid and a liquid insulation is the most frequently used insulating system in high voltage apparatus, where components have to he insulated and loss heat has to be dissipated. The requirements on the liquid part of the insulating system are not only the electric and dielectric performance but also the performance regarding environmental requirements and dehydration capability as well as low in flammability. The use of ester liquid midel 7131, partly or totally replacing mineral oil, reduces the risk of environmental pollution, increases the lifetime of the component and reduces the fire risk. In distribution transformers midel 7131 has been used for several years with very good experience and therefore the manufacturer are encouraged to use midel 7131 also in power transformers even if the viscosity of the new liquid is higher than the viscosity of mineral oil. Due to larger dimensions of power transformers in comparison to distribution transformers special consideration is necessary. Some results concerning the electric and dielectric behaviour of midel 7131 is presented and pure midel 7131 as well as mixtures with mineral oil fulfil the requirements on the electrical performance of liquid insulating materials.