Method for evaluation of impregnant compatibility with lead-wire insulation

Abstract

The most important component from the point of view of the life of each electrical equipment is its insulation system. The basic insulation of the electrical system is primary and secondary insulation. Primary insulation is the first insulation layer applied directly to the electric winding wire. Solvent varnishes are insulating materials of primary insulation and their role is in particular to provide electrical strength of the wire. Secondary insulation, often called as secondary impregnation, is the winding insulation process that follows primary insulation. It is a chemical process where the mechanical stability of the electrical windings increases by applying impregnants and insulated wires are protected against mechanical damage, moisture and other environmental influences. The role of impregnants in the winding of electrical machines is mainly the reinforcement of winding and heat removal. The influence of impregnant on the electrical insulating properties contributes significantly to the life of the insulation system with impregnant: compatibility with wire enamel, compatibility with other materials of insulation system according to construction and type of motor or transformer. The problem may also be the insufficient compatibility of the impregnant with the wire insulation. Therefore composition and processing of wire insulation has a significant impact on quality of impregnation.