Thermosetting organic resins are widely applied as insulating coatings for soft magnetic powder cores (SMPCs) because of their high electrical resistivity. However, their poor thermal stability and thermal decomposition lead to a decrease in electrical resistivity, thus limiting the annealing temperature of SMPCs. The large amount of internal stress generated by soft magnetic composites during pressing must be mitigated at high temperatures; therefore, it is especially important to find organic resins with excellent thermal stabilities. In this study, we prepared SMPCs using poly-silicon-containing arylacetylene resin, an organic resin resistant to high temperatures, as an insulating layer. With 2 wt % PSA as an insulating layer and annealed at 700 °C for 1 h, the FeSiAl SMPCs achieved the best magnetic properties, including the lowest core loss of 184 mW/cm³ (measured at 0.1 T and 50 kHz) and highest permeability of 96.

The effect of different particle size distribution of Fe-6.5 wt%Si powder on the microstructure and soft magnetic properties of the corresponding soft magnetic powder cores (SMPCs) was investigated. By optimizing particle size distribution, the density of SMPCs increased and the total core loss significantly decreased. According to the result of loss separation, density of SMPCs is inversely proportional to hysteresis loss, while with increasing the content of the fine particles, the eddy current loss significantly decreased. It was found that with magnetic powder of particle size-grading as 10%, 10%, 60%, and 20% for particles with size between −75 to +38, −38 to +23, −23 to +13, and −13 μm, respectively, the Fe-6.5 wt%Si SMPCs exhibit optimal comprehensive magnetic performances with the effective permeability of about 60, the percent permeability at 100 Oe is up to 70%, and the lowest core loss of 553 mW/cm³.

Existing research on the magnetic coupler of unmanned aerial vehicle (UAV) wireless charging systems usually ignores the UAV fuselage, but the fuselage causes eddy current loss and reduces a system’s efficiency. Therefore, aiming at the above problems, this paper proposes a design for a magnetic coupler using nanocrystalline cores to reduce the loss caused by the UAV fuselage. First, the parameters of the asymmetric circular coils were designed for higher mutual inductance. The losses caused by the windings and cores were also calculated. Second, for the loss effect of the carbon fiber fuselage, the fuselage was modeled as an additional coil coupled with both the transmitting and receiving coils. The fact that the eddy current induced by the fuselage leads to efficiency reduction is revealed, which has been generally ignored by previous research. Then, the effect of the nanocrystalline alloy was analyzed based on the magnetic circuit model. An optimized nanocrystalline alloy film was applied to reduce eddy current loss and improve coupler efficiency. Finally, an experimental prototype with a 500 W output, 90.3% efficiency, and a 300 mm air gap were fabricated. When compared to the design without UAV material considerations, the coupler efficiency was improved by 7.9%.