In this paper, we present basics of modeling of complex magnetic circuits in electromagnetic devices for the purpose of didactic considerations. In order to help students better understand the physical issues in a magnetic field, an elementary example of the magnetic field in the coil depending on magnetic core construction has been given. The use of modern software tools for numerical calculation of magnetic fields (FEM) provides easier visualization of the problem and calculation of magnetic circuit parameters for magnetic circuit lumped models by using reluctance. The paper presents an educational scale model of the three-phase three-winding transformers with specially designed coils to provide increased leakage magnetic fluxes and spaces for magnetic field measuring probes