Research on the Thermal Aging Characteristics of Epoxy Resin for High Frequency Transformers Based on Activation Energy

High frequency transformer is one of the core components of power electronic transformer, in which epoxy resin is the main solid insulation component, and its insulation performance is easy to fail under the action of long-term thermal stress. The thermal aging of epoxy resin is a slow chemical reaction process. Activation energy, as the inherent property of the insulation state of materials, can effectively evaluate the aging state of materials. In this paper, the activation energies of different aging stages at different aging temperatures were calculated based on Thermogravimetric method. The results show that the change in the activation energy of epoxy resin after thermal aging depends on both the aging stage and environmental conditions. In the case of short-term thermal aging, the activation energy may increase due to enhanced crosslinking. In contrast, during long-term thermal aging, the activation energy may significantly decrease as a result of chemical bond breakage and oxidation. However, the mechanism that the activation energy of epoxy resin is higher than that of non aged epoxy resin after thermal aging above the glass transition temperature is still unclear and needs further study.