Nanocrystalline material development for high-power inductors

A new high-saturation induction, high-temperature nanocomposite alloy for high-power inductors is discussed. This material has FeCo with an A2 or B2 structure embedded in an amorphous matrix. An alloy of composition Fe56Co24Nb4B13Si2Cu1 was cast into a 1.10in. wide, 0.001in. thick ribbon from which a toroidal core of approximately 4.25in. outer diameter, 1.38in. inner diameter, and 1.10in. tall was wound. The core was given a 2T transverse magnetic field anneal, and impregnated for strength. Field annealing resulted in a linear B-H response with a relative permeability of 1400 that remained constant up to field strengths of 1.2T. The core was used to construct a 25μH inductor for a 25kW dc-dc converter. The inductor was rated for operation in discontinuous conduction mode at a peak current of 300A and a switching frequency of up to 20kHz. Compared to commercially available materials, this new alloy can operate at higher flux densities and higher temperatures, thus reducing the overall size of the inductor.