Generator Simulation-Model Constants by Finite Elements: Comparison with Test Results

This paper describes the development and validation of a process combining finite element techniques and improved equivalent circuit analysis methods to find circuit data for a generator directly from the generator design. This work was accomplished under EPRI Research Projects RP1288 and RP1513. The process uses non-linear magnetostatic methods to find a steady-state two-dimension flux pattern and next, a linear diffusion method to find the small-signal frequency response of the generator in terms of frequency-dependent operational inductances, such as lfd(s) and lddo(s). Correspondence of the small signal inductances to small perturbations around the given load point is ensured through the use of incremental permeabilities. The incremental permeabilities are assigned to match the local steady-state flux density, obtained from the initial magnetostatic load-point solution. The equivalent circuit model data are found by multi-variable curve fitting techniques, simultaneously fitting the rotor, stator, and field circuit constants to the operational inductance data.