Accurately Disentangling Core and Winding Losses in Experimental, In-Situ Magnetic Loss Measurement for Power Electronic Circuits and Applications

This article presents a new idea that enables direct, high-precision, in-situ, and in-operation core loss measurement in experiment. Coupled with the improved dual-curve derivative (iDCD) method that provides accurate in-situ total magnetic loss measurement, this article can accurately and experimentally disentangle the core and winding losses from the lumped magnetic loss in-situ and in-operation for practical power electronic converters. Historically, the timing skew between measurement channels has plagued direct power loss measurement approaches, especially for switched-mode power electronics whose voltage and current waveforms are both alternating current (ac) (e.g., excited by rectangular and triangular stimuli). This unknown timing skew severely hinders the application of the conventional “two-winding method” for magnetic core loss measurement, introducing challenges when attempting to measure the power loss under desired operating conditions. This article builds a comprehensive mathematical model to analyze the effect of the timing skew on the direct core loss measurement and presents a novel approach based on a capacitor branch to eliminate the measurement error caused by the unknown timing skew. The proposed method provides an extremely tight error tolerance at a sub-1% level. A new cross-validation method—though is only suitable in highly controlled lab settings and is less accurate—is developed to demonstrate the proposed method’s efficacy and prove that the proposed method can be freely applied beyond lab settings. Theoretical analysis is verified in simulation and experiment with a conventional dc-dc step-down buck converter with nonsinusoidal voltage and current waveforms under a range of practical circuit parameters.