End turn corona suppressing coatings their composition and effect

Many techniques have been proposed for the elimination of the ring of corona which can occur just outside the slot of high voltage stator coils. The aim of this work was to evaluate these voltage grading methods to determine the most practical methods of accomplishing this objective for machines rated above and below 16 KV. For operating voltages up to 16 KV a single semiconducting silicon carbide paint system of 2.5″ or longer provides excellent corona protection. For higher voltages a multiple paint system or a system composed of two layers of paint separated by insulation is required.