This work presents a Finite Element Method (FEM) modeling of a 3-phase, 11/0.4 kV, 50 Hz, oil immersed, core (stack) type distribution transformer. In this work The ANSYS package is used to build the finite element model of the transformer, using actual transformer parameters. To investigate transformer performance several analyses are accomplished on this model such as; static analysis, transient analysis, harmonic analysis. Two types of analysis are considered; the linear analysis (using constant permeability) and the nonlinear analysis using the B-H curve of iron. The results are presented in 2D vector and contour colored plots of the FE model, the voltage and current curves, the magnetic flux lines, flux density, field intensity, current density, and magnetic forces.