GB974189A - Inductive apparatus - Google Patents

Abstract

974,189. Transformers. WESTINGHOUSE ELECTRIC CORPORATION. Aug. 14, 1962 [Sept. 29, 1961], No. 31132/62. Heading H1T. A coil for inductive apparatus such as a transformer comprises an insulating tube carrying a winding on which is a second insulating tube carrying a second winding, the windings being wound with an insulated conductor having a coating 204 (Fig. 5) over the enamel insulation 202, the coating being non-tacky at ambient temperatures but becoming soft at higher temperatures and flowing to bond the turns of the windings together and improve the dielectric characteristics of the coil. A transformer coil wound with rectangular and circular wire as described above is shown in Fig. 1. The low voltage winding has inner layers 12, 16 on a paper former 10 with thermally stabilized paper insulation 18, 20 and outer layers 42, 44 with paper insulation 40, 46, 48. The paper interleaved high voltage winding is in three sections 28, 36, 38 separated by ducts 32 formed by corrugated fibrous sheet 30. Between the low and high voltage windings is paper insulation 26, 40 and ducts 24 formed by spacers 22 for a liquid dielectric. The paper insulation except the paper layers between the high voltage winding layers which are crimped at the ends has a discontinuous coating on one or both sides of material similar in action to the outer coating on the wire. After winding the coil is heated under pressure to 150‹ to 175‹ C. which causes the coatings on the paper and wire to become soft and flow. The coil is then cooled and the coatings permanently harden to form a solid unit. A transformer coil is described (Fig. 3, not shown) with only one section of low and high voltage windings. The coating material may be epoxy resin, phenolic, epoxy phenolic, high molecular weight vinyl formal, vinyl formal plus epoxy resin or other suitable resins. The enamel insulation may be urea formaldehyde plus vinyl formal plus epoxy resin enamel.