Performance Comparison of Finemet and Metglas Tape Cores Under Non-Sinusoidal Waveforms With DC Bias

In a previous paper, we introduced a modified Steinmetz equation to account for dc-bias field effects, which requires only a simple dc permeability measurement to predict total power loss. In this paper, we expanded our investigation to include Finemet nanocrystalline material and found that our modified Steinmetz formalism was effective in predicting dc-bias-related losses for this system as well. In this paper, it was observed that Finemet cores exhibit lower losses than Metglas cores under identical test frequencies and bias fields. In addition, we show that a full characterization of the dc loss component necessitates the consideration of higher order (n>1) harmonic components. In order to quantify these higher frequency loss components, a dc-dc converter-based test system was built to intentionally introduce inductor current harmonics by varying the filter capacitance and parasitic inductance of the test system. Both core types were evaluated under fundamental frequencies of 20 to 150 kHz and dc-bias fields of up to 1.3 kA/m, with the inclusion of distorted waveforms obtained by varying filter capacitance. At higher frequencies, the Metglas cores were found to exhibit greater loss fractions associated with the higher order harmonic components. A detailed summary of the measured core loss characteristics for both core types is included and discussed. This paper includes the details of the measurements, the modified Steinmetz relation, and the loss extraction algorithm used for analysis.