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

In this study, to decrease coercivity and iron loss for the Fe–Si–B–Nb–Cu–C nanocrystalline powder-pressed magnetic core for hundreds of 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 pressing the powder. In addition, a 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, a coercvity of 123 A/m, a relative permeability of 32.5, and iron losses of 105 kW/m3 at 100 kHz, 50 mT, and 2194 kW/m3 at 1 MHz, 50 mT. From the iron loss breakdown 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
$47\times 44\times16$
mm, a dc coil resistance of 7.3
$\text{m}\Omega $
, an inductance of
$12.1 ~\mu \text{H}$
, a
$Q$
-factor of about 127 at 1 MHz, and an inductance drop of 4.1% at a superimposed dc current of 30 A.