A time-domain parameter calculation of a turbogenerator state-space model is presented. The finite-element (FE) method has been used to simulate a two-dimensional (2-D) nonlinear transient condition of the turbogenerator. An open-circuit transient excitation of the machine in closed-loop conditions (excitation system and unloaded synchronous generator) was reproduced to extract flux linkages, power losses, and eddy currents produced within the generator, which allowed the computation of the parameters of an electrical circuit. An electrical circuit structure with one d-axis damper winding is proposed. New parameter behavior profiles were found for the fictitious damper winding, and the saturation effects on the field winding reactance were determined. FE commercial software is employed during the research as a validation tool. It is found that the simulated time-domain response of the lumped model closely follows the time-stepping FE model. The research was carried out for a large turbine generator of 150 MVA, 13.8 kV, 50 Hz, and two poles.