Fabrication of Fe-Based Nanocrystalline Powder-Pressed Magnetic Core and Application to Planar Reactor for Hundreds of kHz or Beyond

Abstract

In this study, to decrease coercivity and iron loss for the Fe-Si-B-Nb-Cu-C nanocrystalline powder-pressed magnetic core for hundreds kHz or beyond, a post annealing after pressing the Fe-Si-B-Nb-Cu-C amorphous powder was executed for nanocrytallization and release of the residual strain induced through the pressing the powder. In addition, novel fabrication procedure for obtaining the small coercivity powdered magnetic core was proposed. It was found that the fabricated Fe-Si-B-Nb-Cu-C nanocrystalline powdered magnetic core exhibited a saturation magnetization of 0.91 T, coercvity of 123 A/m, relative permeability of 32.5 and iron losses of 105 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 100kHz, 50mT and 2194 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 1MHz, 50mT. From the iron loss break-down for the fabricated Fe-Si-B-Nb-Cu-C nanocrystalline powdered magnetic core, its hysteresis and eddy current losses were smaller than those of Fe-Si-B-C-Cr powder-pressed magnetic core. In addition, a planar reactor was fabricated using the powder-pressed magnetic core, which had a size of 47×44×16 mm, DC coil resistance of 7.3mΩ, inductance of 12.1 μH, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -factor of about 127 at 1MHz and inductance drop of 4.1% at a superimposed DC current of 30A.