Using different types of finite elements in electrical machines thin airgaps

The moving band technique has been used since the 1980s as an efficient method to perform the movement in the analysis of electrical machines. However, the elements distortion and the reconstruction of their connections create discontinuities on the electromotive force. This problem can be avoided by choosing a time step that does not allow elements distortion. In dynamics problems or with electronic circuits the time step is variable and such a condition is difficult to reach. In the electronic circuits, with diodes for example, the time step has to be strongly reduced to ensure correct switch transitions. The numerical errors due the elements distortion and reconstruction of their connections depend on: the way how the motion is made ( cuts, transition instants, etc); the geometry of moving band elements; the type of finite elements used; the order of interpolation functions; and the refinement of the finite element mesh. This paper presents an efficient way to use the moving band technique by considering the above key factors.