Effect of high permittivity and core dimensions on the permeability measurement for Mn-Zn ferrite cores used in high-frequency transformer

This paper presents an experimental method and theoretical analysis to study the dielectric effect in Mn-Zn ferrite cores. Experimental results show that dielectric effect becomes very pronounced at high frequency. This is caused by the high permittivity of the ferrite core. Theoretical analysis is then introduced to study the influence of high permittivity on the permeability measurement. Numerical results show that significant aberrations of measured permeability from its intrinsic value could occur due to the high permittivity in the Mn-Zn ferrite cores.

1. Introduction

Mn-Zn ferrite cores are used widely to construct high-frequency transformers for power electronic circuits. In recent years, it finds new applications in coupling circuit for low-voltage power-line communication. The permeability of such cores is one of the important information when such high-frequency transformers or coupling circuits are designed.