Stability of the electrical resistance and mechanism of conductivity of the composite semiconducting materials

Summary form only given. Semiconducting composite materials with electrical insulation matrix and semiconducting fillers have been investigated with the aim of producing them with stable resistance for equalizing electrical field intensity in high-voltage turbogenerator winding insulation. For semiconducting fillers, different kinds of silicon carbide powders (SiC), soot carbon, and copper-bearing glass fiber tape have been used. For insulation binder ternary epoxy compounds and oil-glyptal enamel have been used. The mechanism for the operation of semiconducting compositions has been analyzed on the basis of obtained dependencies of the magnitude of the electrical resistance and its non-linear coefficient from electrical field intensity for compositions with different concentrations of semiconducting fillers, and by its correlation with a mathematical model of conductivity for semiconducting grain conglomerate. On the basis of the understanding of the two mechanisms: (i) the semiconducting structure formation and (ii) the operation such compositions, semiconducting materials with stable characteristics have been developed. The stability of the materials developed has been confirmed by testing and using them for a long time in high-voltage winding of the turbogenerators and hydrogenerators, produced by the Large Electrical Machines Plant “Electrotyazhmash” (Kharkov, Ukraine/), where this work was done