GB973433A - Improvements in gas-cooled electrical machines or apparatus having connection through-bolts coated with electrically insulating material - Google Patents

Abstract

973,433. Carrying conductors through partitions; mounting terminals. ALLMANNA SVENSKA ELEKTRISKA A.B. Feb. 10, 1961 [Feb. 13, 1960], No. 4988/61. Heading H2E. A gas-cooled electrical machine or apparatus is provided with a metallic connection throughbolt and electrically insulating material surrounding the bolt, the insulating material comprising a solid resin derived from a completely polymerizable resin, applied around the bolt, and reinforced with synthetic organic fibres applied around the bolt in extended state obtained during manufacture and which shrink when subjected to heat during curing of the resin. If cold-setting resins are used the heat evolved by the setting reaction is sufficient to shrink the fibres. A completely polymerizable resin is a completely reactive polymerizable composition such as a solventless resin or a resin containing a solvent which is completely reactive with the resin. As shown, part of the casing 4 of a hydrogen-cooled electrical machine is provided with a metallic through bolt 1 surrounded by insulating material 2 making a gas-tight seal with the bolt. Rubber sealing rings 5 from a gas-tight seal between the insulated bolt and the internal wall of the bore 3 in the casing, the rings being pressed between a washer 6 and a spacing ring 8 by a collar 7 screwed into the bore. The spacing ring is prevented from rotating by a projecting screw 9 which engages an axial groove 10 in the bore. In the many examples unsaturated polyester resins and epoxy resins are included as suitable completely polymerizable resins, while suitable fibres are of polyethylene glycol terephthalate, polyvinylidene chloride, polyacrylonitrile, polyamides, and cellulose-based materials, the molecules in these fibres being formed in an extended state during the normal process of manufacture. The fibrous material may be applied as tape or yarn, and the resin may be impregnated into this material before its application to the bolt, applied between layers of fibre as it is applied to the bolt, or impregnated with or without vacuum into a completed winding. The bolt may be given a thin coating of silicone rubber or other elastic material before the application of the reinforced resin, and to a limited extent the resins used may be mixed with powders or grain-shaped fillers such as quartz powder or mica powder.