Abstract: In order to offer the epoxy resin composition allowing much lower viscosity and higher heat resistance (glass transition temperature) of cured product to coexist and lowering hygroscopic property, and the insulation coil and one-piece impregnation type rotating machine with improved insulation performance using the composition, the epoxy resin composition made of a mixture of 1 to 5 by weight of sulfonium salt cationic polymerization initiator and 3 to 15 by weight of reactive diluent with 100 by weight of epoxy resin is provided. The insulation coil that is an insulation coil made of plain conductor wire formed into a specified shape and wound with insulation material, impregnated with the epoxy resin composition and then cured is provided.

Abstract: A method of manufacturing electrical windings, according to which it is possible to manufacture, with high efficiency, the electrical windings differing in function and capable of performing the functions required of the respective windings. In the steps of forming the windings by winding the conductors and applying insulation on the windings, there are formed the insulating layers 12, 22 and 32 suitable for the respective types of windings, viz. main pole coil 10, interpole coil 20 and compensating coils 30, and a same impregnating resin is impregnated and hardened in each of said main pole coil 10, interpole coil 20 and compensating coils 30.

Abstract: In the production of electrically insulated coils which make up insulating layers, insulating material is wound around an electric conductor to form an insulating substrate, then impregnating varnish consisting of thermosetting resin is applied to the insulating substrate and hardened. In this electrically insulated coil production method, the impregnating varnish is made up of acid anhydride setting epoxy resin elements that include latent accelerators. These accelerators take more than 30 days to increase their initial viscosity by three times during storage at 25 degrees centigrade. After the insulating substrate is impregnated with the varnish, the substrate is heated at a temperature which will cause the impregnating varnish on the surface of the insulating substrate to lose its fluidity in under 30 minutes in order to preset the varnish.

Abstract: Electrically insulated coils having excellent moisture resistance or water resistance utilize a simple material that is readily available. Using a simple method of manufacture, rotating electric machines such as motors for driving pumps, traction motors for rolling stocks and the like suitable for use in the outdoors may be built with the electrically insulated coils. The coils are coated with a fluorine-containing coating at least on portions which are exposed out of the side of the core. Since a uniform hydrophobic layer utilizing the repellent action of fluorine atoms is capable of being provided on the surface of the electrically insulated coils, the electrically insulated coils and the rotating electrical machines incorporating them feature excellent moisture resistance and water resistance.

Abstract: An electrically insulated coil manufactured with a composition comprising a poly-functional epoxy resin having at least three of p-(2,3-epoxy propoxy) phenyl groups and a bi-functional epoxy resin as a binding resin for a reinforced insulating base sheet and as an impregnation resin has no peeling off in its insulating layers and is capable to be used continuously under the temperature at 200.degree. C. or above.