Measurement and loss model of ferrites with non-sinusoidal waveforms

Abstract

The usual data of commercial ferrite grades are given for sinusoidal waveforms, although the voltage in the typical applications in power electronics resembles to square waves. Firstly, an accurate two wire, oscilloscope power measurement is presented. Special wide frequency current and voltage transducers were designed, with a very low phase difference up to 50 MHz. Secondly, a ferrite loss model named natural Steinmetz extension (NSE) is presented. The model is checked with measurements on two different ferrite grades, with square waves with a large variation in duty ratio. The proposed model is compared with modified Steinmetz equation (MSE). The two methods with a different mathematical formulation give comparable but different results.