A novel approach to model the coupling (loading effects) in transformers feeding switching loads is presented. In this approach transfer functions and nonlinear V-I relationships are used to model a voltage source excited three-dimensional transformer model. Three load cases of the transformer model are considered: (1) no load, (2) linear load, and (3) rectifier load. The results obtained from the three load cases demonstrate that coupling (loading) effects are accounted for in the modeling approach.