FEM Simulation of Effect of Non-Uniform Air Gap on Apparent Permeability of Cut Cores

The paper describes results of two-dimensional finite element modeling of cut (gapped) magnetic cores. The influence of an irregular air gap on the apparent permeability of the core is calculated. Two magnetically soft materials are used: electrical steel M-27 and supermalloy (80% Ni). The results indicate that decreasing the minimum air gap between parts of the core can increase the initial effective permeability of the core, by a factor of 2 or 3 times despite the total volume of the gap remaining unchanged.