COMPARISON OF EXACT AND APPROXIMATE FINITE-ELEMENT SOLUTION OF THE TWO-DIMENSIONAL NONLINEAR EDDY-CURRENT PROBLEM WITH MEASUREMENTS

The comparison of two methods for the numerical solution of two-dimensional nonlinear eddy-current problems using the finite element method is presented. An exact solution is obtained by time-step calculation; all influences except iron hysteresis are taken into account. The second method is limited to the solution of quasi-stationary problems; the solution is based on the assumption that all field quantities have sinusoidal time variation. The field dependence of the permeability is considered approximately by introducing an effective permeability, only dependent on the amplitude of the magnetic flux density, in this case. The numerical results are compared with measurements and, in addition, the influence of wave shapes on the accuracy of the results obtained by the approximate method is examined and discussed.