Finite Elements for Three-Dimensional Magnetostatic Fields and its Application to Turbine-Generator End Regions

This paper presents a general finite element solution of magnetostatic fields due to three-dimensional current sources, in axisymmetric geometries, in terms of the scalar magnetic potential. In the space occupied by the current sources, and there only, a correction field defined by a vector quantity must be added to the scalar potential field. Numerically, this correction field is obtained by using a vector potential which may be allowed to be divergenceless in the mean. Since the correction field is non-zero only in the current-carrying space, it is computationally relatively inexpensive to find. This method is used to predict the open-circuit and short-circuit magnetic fields in the end region of a turbine-generator. In order to assess the accuracy of the process, the magnetic fields are calculated and compared with the classical current-sheet approach and test measurements.