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AssigneeALSTOM Technology Ltd
InventorsThomas Baumann, Johann Nienburg, Jorg Oesterheld, Jorg Sopka
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It is an object of the invention to provide a process for producing insulations for electrical conductors by means of powder coating, which results in aging which is improved compared to glass-mica or casting-resin insulation. It is also intended to describe a powder which is suitable for such a process. For this purpose, the powder is applied a number of times in succession, in the form of individual layers which follow one another, until a layer thickness of ≦10 mm is reached, and each of the individual layers undergoes intermediate heat curing before the next individual layer is applied. The intermediate curing of each individual layer uses a curing time which corresponds to 2-10 times the gel time of the powder used. Finally, the entire insulation undergoes final curing. The result of an electrical life test carried out on various specimens insulated with epoxy-resin powder which contains fine filler and has been applied in accordance with the invention is illustrated in the only FIGURE.
A process for producing insulations for electrical conductors by means of powder coating, on the basis of thermosets, characterized in that
The process as claimed in one of the preceding claims, characterized in that powders of different composition are used to apply the individual layers.
The powder as claimed in one of the preceding claims, characterized in that the coarse filler has a mean grain size d50 of approximately 10 μm.
The powder as claimed in one of the preceding claims, characterized in that the inorganic filler content is approximately 40 percent by weight.
The powder as claimed in one of the preceding claims, characterized in that the fine filler and the coarse filler are fillers with a different hardness.
The powder as claimed in one of the preceding claims, characterized in that the fine filler and/or the coarse filler are mixtures of fillers of the same or different hardness.
The powder as claimed in one of the preceding claims, characterized in that the coarse filler has a Mohs hardness of at most 7.
The powder as claimed in one of the preceding claims, characterized in that the coarse filler has a Mohs hardness of ≦4.
The powder as claimed in one of the preceding claims, characterized in that the fine filler is selected from TiO2, ZnO or SiO2, and in that the coarse filler is selected from CaCO3, wollastonite and talc.
The powder as claimed in one of the preceding claims, characterized in that in the cured state the thermoset has a glass transition temperature of at least 150° C.
The powder as claimed in one of the preceding claims, characterized in that the resin-hardener-auxiliary system of the thermoset is such that it cures without releasing volatile substances.
The powder as claimed in one of the preceding claims, characterized in that the thermoset is an epoxy resin.
The powder as claimed in one of the preceding claims, characterized in that the coarse filler has a hardness which is approximately one unit of Mohs hardness below that of the materials of the conveying and processing means which are in contact with the filler.
Dependencies are inferred from the claim text.