This article presents a new generalized non-linear dynamical model of a transformer with saturation and hysteresis effects. The structure of this new model is based on a magnetic equivalent circuit with non-linear reluctance elements. Using this method, accurate models of three- and five-legged transformers with magnetic saturation and hysteresis phenomena of iron core are introduced and inrush current in normal and sequential phase energization techniques are evaluated. Moreover, the effects of neutral resistance, magnetic structure and winding connections on inrush current are determined. In addition, for validation of the proposed model, some numerical simulations are made and compared with other techniques. Simulation results illustrate that the proposed model has high accuracy and efficiency for non-linear dynamical modelling of a transformer.