Effect of Epoxy Cracking on Stability of Impregnated Windings Related to Thermal and Mechanical Properties

Abstract

The anisotropy of thermal conductivity induced by epoxy cracking in impregnated windings have been studied in order to estimate the stability change. Epoxy cracking or debonding have been found to release the stored elastic energy as the form of heat which could cause the premature quench of the impregnated windings. Furthermore it would degrade not only the macroscopic mechanical properties but also thermal properties. The change of macroscopic mechanical properties was measured in terms of the load-displacement curves of the windings and the stress analysis was made by finite element method. The change of heat dissipation rate was measured using the heater and thermo-couples which were installed in the windings. The temperature distribution was also measured. The stability of the windings are discussed based on mechanical and thermal properties and the effect of induced epoxy cracks will be studied.