Finite element prediction of steady state operation of a turbine-generator using conductivity matrices

A two-dimensional cross-section of a turbine-generator is modelled using first order finite elements formulated by the nodal method. Design information is used to calculate the excitation current and load angle corresponding to any terminal voltage, current and power factor. A two-phase winding with sinusoidally distributed turns replaces the 3-phase stator winding. This leads to the use of conductivity matrices for the stator windings which allow the field distribution, stator current magnitude and position to be calculated simultaneously. Newton-Raphson iterations are required to obtain correct iron permeabilities for the saturable elements, Calculated load angles and excitation requirements compare well with test results on a 500MW turbine-generator. The method is simple and converges with few iterations.