Improved Soft Magnetic Materials for High Power Density Electrical Machines

CMU and Magnetics, A Division of Spang and Co. have developed a new high-saturation induction, high-temperature nanocomposite alloy for high-power inductors. This material has FeCo nanocrystals with an A2 or B2 structure embedded in an amorphous matrix. Field annealing resulted in a linear B-H response with a relative permeability of 1400, constant up to fields of 1.2 T. The material was used in a 25 µH inductor for a 25 kW DC-DC converter rated for operation in discontinuous conduction mode at a peak current of 300A and a switching frequency up to 20 kHz. 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. A recent scientific focus has been on Co-rich nanocomposites which sacrifice some induction for improved mechanical properties, stronger response to magnetic field processing, and potentially lower losses and magnetostriction. These are subject of a provisional patent and proposed for further development. BENEFIT: Soft magnetic materials that have good Bsat, long term stability above 200C, and low losses above 50 kHz will find use in demanding applications where forced cooling is impractical or space is at a premium. Materials that exhibit these traits could trade off higher core losses for the ability to operate at higher flux density levels and result in smaller components. Applications could include automotive, downhole drilling, aircraft and power conversion.