Soft magnetic properties of Fe-Ni powder cores in the high frequency range

Fe-Ni cores are excellent candidates for switching regulator inductors, transformers, reactors and in-line noise filters. Herein the influence of the phenol binder content on the microstructure and magnetic properties of Fe-50 wt% Ni powder cores in the high frequency range is investigated. Regardless of the binder content, all cores form a disordered A1 phase. The saturation magnetization (4 pi M-s) and initial permeability increase as the binder content decreases. The core with a binder content of 0.5 wt% shows a relatively high 4 pi M-s of 1.38 T and the highest permeability value of 70.9. Moreover, the total core loss (P-cv) with frequency ranges from 5 kHz to 1 MHz under a magnetic flux density of 10 mT depending on the binder content. A binder content of 3.0 wt% significantly reduces P-cv in the high frequency range above 100 kHz. At a frequency of 500 kHz, the P-cv values are 154.9, 128.7, and 133.8 kW/m(3) for the cores with binder contents of 0.3, 0.5, and 1.0 wt%, respectively, but the value drastically decreases to 60.5 kW/m(3) for a binder content of 3.0 wt%. Thus, the binder, which acts as an insulator layer between particles, affects the eddy current and consequently, P-cv. These results demonstrate that Fe-Ni powder cores exhibit excellent soft magnetic properties at various frequencies and suggest that a binder content of 3.0 wt% may realize optimal properties for future high frequency applications.