HIGH-TEMPERATURE ELECTRICAL INSULATING INORGANIC COATINGS ON WIRE

摘要

The program on high-temperature electrical insulation on wire in its third and final year, covered the work on flexibility of coated wire, coating trials on clad copper wires, firing procedure for two coats of 58C on copper wire, vitreous silica and boron nitride mill additions to glass coating 58C, and vitreous coatings sheathed with organics. Also as a part of the last years efforts test data were obtained on high-temperature insulated wire supplied by various manufacturers.nFlexibility studies indicated the ratio of coating thickness to wire diameter and the cooling cycle were important factors affecting flexibility of the coating. It was demonstrated that a heat treatment of the coating may increase coating flexibility. Contrary to what was expected, coatings on inconel-clad copper wire did not show an increase in flexibility over coatings on plain copper wire.nThe results of coating trials on inconel-clad, stainless steel-clad (Oxalloy), nickel-clad (Kulgrid), silver-clad, and aluminum-clad copper wires are given. A firing study of coating 58C resulted in the optimum firing procedure for two coats of 58C on copper wire.nIt was demonstrated that additions of vitreous silica and boron nitride to the mill formula of coatings 58 and 58C enhance the electrical properties of the resulting coating.nSheathing of vitreous coatings with organics showed promise as a method of retaining the flexed vitreous coating on the wire. It was thought that in service the organic coating may burn off at a temperature where the vitreous coating could be capable of sealing itself.nElectrical tests of flexed coated specimens indicated that room temperature dielectric constant and dissipation factor were not sensitive to the first fine cracks which appeared.