A Practical Method to Measure Electrical AC Conductivity of MnZn Ferrites Using Conventional Toroids

In this paper, a new method to construct ac electrical properties from impedance measurements using conventional ring core specimens is proposed. Different coaxial cartridges are developed allowing four-wire measurements with an automatic compensation of the test-leads. To achieve optimum results, the specific material parameters are reconstructed from the measured impedances by means of an analytical solution of Maxwell's equations for the toroidal sample geometry. Hence inhomogeneous electromagnetic fields due to occurring eddy currents and displacement currents are considered up to the megahertz range. To investigate the influence of the temperature on the electrical properties, the temperature-resistant cartridges can be transferred into a heating cabinet-specific results are finally exemplified for different MnZn ferrite materials.