Crystal-like microstructural Finemet/FeSi compound powder core with excellent soft magnetic properties and its loss separation analysis

Abstract

The Finemet/FeSi compound powder cores with crystal-like microstructure were successfully fabricated by adding micron-size gas-atomized FeSi powders into the thick Finemet flaky-powders. Loss-separation fitting model for the compound cores mixed with different mass fractions of FeSi powders was built to analyze the relative loss mechanism and source of each part loss. Due to the fact that the magnetic powders were coated with high-quality electrical-insulating layer, the inter-particle eddy current energy loss is only 1/400–1/800 of total energy loss. The volume fraction of non-magnetic phase and pinning effect, which are found to be sensitive to density of cores, play a significant role on both hysteresis loss and excess loss. As compared to the pure Finemet based powder cores, the Finemet/FeSi compound cores mixed with 10–14 wt% of FeSi powders exhibit a higher permeability and a greater retained permeability at a DC-bias field of 7960 A/m. The total core loss reduced from 788 kW/m3 to 614 kW/m3 at 300 kHz, 0.05 T. These results indicated that the Finemet/FeSi compound powder cores with crystal-like microstructure have a great advantage in power electronics applications, and suggested that the powder micro-structure design is a promising method to further improve magnetic performances for soft magnetic composites.

Keywords

• Crystal-like microstructure
• Compound powder cores
• Loss separating fitting model
• Low core loss
• High permeability