Synergistic Enhancement of Electrical‐Thermal Properties in KH550/G‐POSS Functionalized BN/Epoxy Composites for High‐Frequency Transformer Insulation

ABSTRACT With the growing integration of renewable energy and DC power electronics, power electronic transformers (PETs) are vital in AC/DC hybrid grids. Their core component, high‐frequency transformers (HFTs), operates under severe electrical and thermal stresses, such as high dv/dt, high switching frequencies, and elevated temperatures that exceed the limits of conventional epoxy (EP) insulation. These limitations necessitate advanced materials with improved thermal conductivity and electro‐thermal stability for multi‐field conditions. To address this challenge, a synergistic enhancement strategy was proposed by integrating BN nanofillers functionalized through a two‐step KH550/G‐POSS modification. This interface design enables simultaneous regulation of dielectric behavior, heat transport pathways, and processing characteristics. An optimized formula with 7 wt.% G‐POSS content, and 20 vol% BN@G‐POSS nanofiller loading promises an improved thermal conductivity (492.5%) and a reduced viscosity (3493 mPa·s) compared to traditional BN/EP. Furthermore, the composite exhibits robust resistance against electro‐thermal degradation under a 100 kHz electric field, as demonstrated by a significantly elevated partial discharge inception voltage (increased by 266.5 V) and a remarkably attenuated total discharge amplitude (decreased by 256.5742 V). Overall, the BN@G‐POSS/EP system shows strong potential for next‐generation HFTs and PETs, underscoring the importance of interdisciplinary material design in addressing reliability challenges in modern power electronics.