Corona Resistance Enameled Winding Wire

A corona-resistant wire enamel composition is a polyimide, polyamide, polyester, polyamideimide, polyesterimide, or polyetherimide resin and from about 1% to about 35% by weight of dispersed alumina particles of a finite size less than about 0.1 micron, the alumina particles being dispersed therein by high shear mixing. Corona resistant one and two-stage insulations for an electrical conductor insulated with a one or two-stage coating of the wire enamel compositions.

Corona-resistant wire enamel composition which comprises a polyimide, polyamide, polyester, polyamideimide, polyesterimide or polyetherimide resin and approximately 1% to approximately 35% by weight of submicron-sized particles of alumina. The aluminum in the alumina is atomically bound only with oxygen.
It is preferred to employ fumed alumina. The alumina is dispersed in the wire enamel composition with high shear mixing, preferably, in a concentration ranging from about 1 to 20 parts by weight per hundred parts of the resin. The alumina particles are preferably less than about 0.1 micron in size. Also, a method of providing corona-resistant insulation for an electrical conductor employs the above-mentioned composition. The method comprises applying the composition to the conductor, for example wire, by using multi-pass coating and wiping dies and curing between about 330° C. and 370° C., at varying speeds.

Using corona-resistant materials as the enameled wire insulation of variable frequency motors is one of the important ways to extend the service life of variable frequency motors. Most Corona Resistance Enameled Winding Wire is popularly used for home appliances, etc.