Calculation of three-dimensional electromagnetic fields involving laminar eddy currents

The formulation of a method to solve steady-state electromagnetic field problems involving laminar eddy currents is described. Iron nonlinearity is included. The formulation is implemented using finite elements and the problems associated with the solution of the resulting nonlinear equations discussed. Experiments with a Newton-Raphson iteration and modifications to it are described and a best alternative is defined. The matrix equation which requires solution is asymmetric, consequently a matrix equation solver involving the use of a preconditioned incomplete LU decomposition followed by biconjugate gradients has been developed. The application for which the method has been developed is to calculate the stator end-region fields in turbine-generators and examples of the results from this work are presented.