Design Considerations for High-power-density IPT Pads using Nanocrystalline Ribbon Cores

In inductive power transfer, ferrite cores present several drawbacks such as brittleness, low permeability and saturation point, and sensitivity to temperature variation. Other materials such as nanocrystalline alloys are being considered as substitutes. They offer a higher permeability and saturation point. Also, they are more robust and stable with temperature. This paper reviews the design considerations that should be taken into account when designing nanocrystalline cores for IPT applications. Bespoke designs are required to mitigate the eddy-current losses which arise due to the high conductivity of the material. A WPT3 pad, 11 kW, is designed and compared to and identical pad with ferrite cores. Using nanocrystalline ribbon cores, a higher coupling factor, 11%, was achieved. Also, a 2% improvement in efficiency was measured. This is attributed to the lower hysteresis losses and higher coupling factor. Finally, the saturation limits were tested for both materials. Results confirm that, with nanocrystalline ribbon cores, higher power ratings and power densities can be achieved.