Nanocrystalline Core Losses in High Power IPT Systems for EV Charging Applications

This article discusses the effectiveness of the nanocrystalline cores in high-power inductive power transfer (IPT) systems. The core losses and equivalent series resistances (ESRs) of the ferrite and nanocrystalline cores in IPT pads are simulated in ANSYS Maxwell based on measurements of their magnetic properties using the partial cancellation method. Simulated results are verified using experiments of core loss measurements in IPT pads. Both simulated and experimental findings show that the ESR of IPT pads using fractured nanocrystalline cores decreases with higher excitation current, contrary to the typical behaviour of an IPT pad built using ferrite. This behaviour is in accordance with characterisation results of ferrite and nanocrystalline toroids and is analysed using Steinmetz coefficients. A 10 kW IPT system is set up to validate the effectiveness of the fractured nanocrystalline cores. Compared to TDK N95 ferrite cores, an IPT system using non-fractured nanocrystalline cores has a 0.6% reduction in dc-dc efficiency, while that of fractured nanocrystalline cores improves by 0.1% and operates with a lower magnetic flux density within the magnetic core.