| 摘要 |
PURPOSE:To prevent a winding from deformation and to obtain a foil wound transformer having both excellent mechanical strength and high insulating efficiency by a method wherein an air-gap is provided on the metal sheet located in the vicinity of a cooling duct. CONSTITUTION:When a high temperature state is obtained for the purpose of drying a winding, or when the temperature of the winding is raised when a transformer is in operation, a metal sheet 3 extends because it has the coefficient of thermal expansion larger than an insulating sheet 4, and said extension due to thermal expansion is concentrated in the air-gap 20 provided on the metal sheet 3. Especially, if the winding is tightly wound gaplessly by applying an intense winding tension, there is no margin when the winding is going to be extended, and the warpage of winding is concentrated at the part which is physically and mechanically weak such as a cooling duct 6, and the stretch of the entire winding sheet is absorbed by the above-mentioned part. As the air-gap 20 is provided on the metal sheet 3, and all the stretch of winding is absorbed at this part by providing a weak point forcibly, and the generation of deformation on the winding can be prevented.
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