This thesis presents two approaches to the analysis of a single-phase transformer with a virtual air gap. The transformer has embedded four small auxiliary windings that locally saturate the core. These windings change the magnetic characteristics of the core and create a virtual air gap. The methods focus on the computation of the change in the reluctance of the transformer core with local saturation and on obtaining the equivalent length of the virtual air gap. The first approach is based on the finite element method (FEM) and uses a commercially available FEM computer program to simulate and solve the magnetic circuit with and without local saturation. The second one is an analytical method that calculates the equivalent length of the virtual air gap by finding the distribution of the magnetic field in the core produced by the auxiliary windings. The magnetic field calculation is used to obtain the operating point of the core and the change in the reluctance of the core. The results obtained from the FEM and the proposed analytical method are compared with experimental results available in the literature.
