Operational Inductances of Turbine-Generators by the Finite-Element Method

As part of EPRI Program, RP 1288-1, Improvement in Accuracy of Prediction of Electrical Machine Constants, a method has been developed for calculating small-signal, terminal, operational inductances. The method is based on solutions to the magnetic diffusion equation by the finite-element method. To faithfully simulate the behavior of the rotor iron for small signal perturbations, measured values for incremental permeability are used. A finite-element grid tailored to handle the skin effect at frequencies up to 100 hertz has been developed. The paper is semi-tutorial in nature and is intended as a basis for future papers, which will compare the results of calculations by this method to test data. Sample flux plots are given, and examples of the frequency dependence of operational inductances are shown.