Effects of Insulator Resistivity on Eddy Current Loss of Compressed Powder Cores Studied by FEM

Effects of the resistivity of the insulation layer on the eddy current loss of compressed Fe and Fe-6.5% Si powder cores were simulated by using 3-D finite element method. Applied field was abruptly reduced and then kept a constant value with the resistivity of the insulation layer of the compressed cores. Permeability of the Fe-6.5% Si compressed cores was increased with the resistivity of the isolation layer. Eddy current losses of the cores were not reduced continuously with the resistivity of the layer. Instead eddy current loss kept a constant loss when the resistivity is about 10⁵ times higher than that of the particle. Eddy current flows all over the cores at low resistivity while the current was confined inside particles if the resistivity is higher than a critical value. To reduce eddy current loss of the compressed cores with high resistivity, it seems that other factors such as microstructure should be considered.