Characterization and Impact of Large-Signal Dielectric Properties in MnZn Ferrites

A time-varying magnetic flux in a magnetic core generates an induced electric field (Faraday's law of induction). This implies that the dielectric properties of ferrites play a critical role in the behavior of large magnetic cores, affecting the onset and severity of dimensional resonances and magnetic skin effect. Therefore, this paper analyzes small-signal and large-signal dielectric measurement techniques for power ferrites. The dielectric response of the "EPCOS TDK N87" MnZn ferrite is measured with respect to frequency, temperature, and amplitude. It is found that the dielectric properties are only slightly nonlinear. Finally, the impact of the dielectric properties on the wavelength, penetration depth, and total losses is computed with large-signal models. The dimensional effects can lead to a significant increase of the losses (up to 100%).