A Power Loss Measurement Technique for Inductive Power Transfer Magnetic Couplers

A critical aspect of designing an inductive power transfer system is the accurate characterization and prediction of power losses in its magnetic couplers under all operating conditions. Understanding the loss mechanisms and their distribution can help the optimization of the magnetic couplers while also being essential to determining thermal management requirements and optimal control parameters. Previously proposed loss measurement methods are neither able to accurately predict the losses in couplers nor characterize their distribution. As a solution, this article proposes a new experimental method, termed the stepped resonant excitation (SRE) method that can accurately predict the power losses in magnetic couplers operated under practical conditions. In addition, the SRE method is capable of producing better insight to the loss distribution by separately quantifying the winding loss and core loss. Experimental results presented in this article show that the SRE method can predict the core loss of an accurately characterized toroidal inductor with less than 10% error when excited with magnetic fields higher than 50 mT. Additionally, the losses measured using the SRE method in a double-D magnetic coupler match well with finite element analysis simulations conducted using datasheet loss curves at 25 °C.