Force calculation based on a local solution of Laplace´s equation

The finite element method in two dimensions is a common technique to analyse electromagnetic devices. The co-ordinates is given as a series of circular harmonics of Maxwell stress method to calculate forces has an important role in this analysis. To obtain an acceptable accuracy of local field values, higher order elements are required yielding an increased computation time. A local solution of Laplace´s equation with the finite element solution as boundary conditions, promises a higher accuracy than the conventional method. The combination with lower order elements gives a good trade-off between accuracy and computation time. Two different methods are compared in the analysis of two applications. A typical example of a rotating machine with a small air gap, a squirrel cage induction machine, is discussed