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

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.