Enhanced Corona Resistance and Insulation Properties of Enamelled Wire Insulating Varnish Induced by Constructed Dielectric Gradient Structured

ABSTRACT In view of the requirements for high‐performance epoxy resin (EP) enamelled wire insulating varnish in the rapidly developments of new energy vehicle drive motors, the problems of localised electric field concentration due to the unevenness electric field distribution has to be solved. In this paper, to enhance the corona resistance, insulation, and mechanical properties of EP insulating varnish, the function dielectric gradient structure consists of hyperbranched polyester (HBP) inner layer and silane coupling agent (KH‐550) modified graphene oxide (GO) nonlinear layer are proposed. The results show that the introduction of HBP not only adjusts the dielectric constant of the insulating varnish but also increases the breakdown field strength significantly, and with the increase of K‐GO, the nonlinear conductivity of K‐GO/EP insulating varnish becomes more prominent. Simulation results show that the highest field strength of the structural insulating varnish with different dielectric constant gradients is reduced to 16.7 kV/mm, and the field strength difference of the inner layer is reduced to 0.3 kV/mm, which further reduces the electric field aberration of the neighbouring interfaces as compared to the pure EP insulating varnish. This work provides a new strategy for constructing the dielectric gradient structure to meet the high corona resistance and insulating varnish requirements of high‐voltage motor enamelled wire insulating varnish in actual industrial production.