The goal of this work is to develop an efficient numerical model of foil-type windings. An equivalent lumped-parameter circuit model is presented, which is suitable for the computation of the terminal impedance within a broad frequency range and for internal voltage propagation studies. Owing to the special geometrical winding shape, particular attention has been paid to the calculation of the involved lumped parameters where efficient and accurate formulas for parameter determination are presented. The core influence is investigated for the broad frequency range by taking into account the frequency dependency of core material properties. Simulated results compared to measurements show that the proposed equivalent circuit in combination with the applied formulas for parameter determination can be used with full success for the computation of the terminal impedance and internal voltage distribution studies. © The Institution of Engineering and Technology 2015.