Fabrication of Permittivity graded materials applied for electric power apparatus

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Major results obtained from the present research project are as follows :1.An centrifugal method was employed to fabricate large-scaled functionally graded materials (FGMs), and alumina-graded epoxy resin was fabricated from alumina/epoxy mixtures.2.It is found that spherical fillers are preferable than irregular fillers, since the spherical fillers increase the maximum packing fraction attainable in FGMs, and accordingly, attain large range of the variation of dielectric constant.3.The fabrication was conducted under various conditions of centrifugal time and velocity, alumina properties, ratio of the mixture, and so on. Based on results, relationship between the fabrication conditions and the gradient is obtained.4.A coefficient of thermal diffusion of alumina filled epoxy resin was measured as a function of the alumina packing fraction. This relationship was used to calculate the thermal resistivity of FGM. Based on the numerical results, relationship between the profiles of gradien … More t and the thermal resistivity of FGM is quantitatively obtained.5.Solid/solid interface, which will appear in the joints of future all solid substation, was modeled by using the FGM columns fabricated by the authors, and properties of the interface against the lightning impulse voltage was experimentally examined under various interface conditions such as the roughness of the interface, combination of the FGM interface and the uniform interface. Based on the experimental results, it is found that the introduction of FGM on the surface of such interface causes increase of the electrical withstand voltage. However, the roughness of the surface has significant influence on the electrical properties of such surface.6.A novel simulation code, which can simulate movement of particles during the centrifugal process, was developed. In this code, the cumulative distribution of the particle diameters was precisely simulated and the dependency of the drag force on the packing fraction was exactly considered. Comparison between the experimental and numerical results shows that the estimation of profiles of gradient in the packing fraction was conducted with reasonable precision. In the end, the effectiveness of the present simulation code is verified. Less