Recent Progress in Magnet Wire Enamels

摘要

Beginning with organic based synthetic polymer substitutes for natural resins, wire enamels have been developed for added toughness, flexibility, heat stability, and resistance to a variety of environments including moisture, solvents, other resins, and contaminants. In the last three years, development has been concentrated on thermal stability improvement. Many new organic resin enameled magnet wires have emerged having long life expectancies at temperatures in excess of 105C, the hot-test spot temperature of Class A in the AIEE Standard No. 1 classification which currently is being revised to allow use of the materials discussed in this paper. Aside from organic enamels, a series of modified silicone enamels has been offered for magnet wire. This development has had limited success. The present materials need further improvement in mechanical properties. The writers have combined the properties of the modified silicones and polytetrafluoroethylene to produce a magnet wire capable of operation at 250C. with long expected life. The paper discusses this development in brief. The paper adds a note of caution in the trend to accept many new materials solely on the basis of thermal stability without a careful investigation of the mechanical, electrical and chemical properties and their relations to the thermal shock properties of the enamels as applied to magnet wire. An example is given of the possible difficulties which can be expected when a product showing excellent thermal stability, but certain other deficiencies, is used without caution. (Author)