A generalized anisotropic finite element formulation for the characterization of synchronous reluctance motor drives

Frederick Nicomedes Isaac, Marquette University


A generalized tensor two dimensional (2D) finite element (FE) computational model, which fully accounts for "material" and "structural" anisotropy is presented. The results presented show for the first time a method that takes into account the curvature in anisotropic and composite material flux barriers by introducing equivalent reluctivities to evaluate the elements of the reluctivity tensor. The novel approach developed is used to study the effects of accounting for anisotropy on the performance characteristics of an axially laminated anisotropic (ALA) rotor synchronous reluctance motor (SynRM) drive. To predict the performance characteristics of the ALA-rotor SynRM drive system, a computer-aided model which indirectly couples a 2D nonlinear FE algorithm, that accounts for "material" and "structural" anisotropy, to a state space algorithm describing the SynRM drive dynamics was developed. Because of the necessity to accurately predict the SynRM performance, and to rigorously account for space and time harmonics, the natural ABC flux linkage based frame of reference was chosen for the state space model formulation. In the implementation of the coupled magnetic-electric circuit algorithm, inductance profiles, calculated in the 2D-FE algorithm, are used as inputs to the state space model. Under conditions of anisotropy, it was necessary to modify the current-energy perturbation method for the calculation of inductance values to account for the anisotropic effect on inductance values. In addition, post processing algorithms for the calculation of machine parameters such as core losses taking into account the axial rotor structure, were developed. To evaluate the accuracy of the model, simulation results were compared to test data obtained on an ALA-rotor SynRM drive system. This dissertation has successfully achieved its objectives by demonstrating that an improvement in the accuracy of the models are attainable by the inclusion of the "material" and "structural" anisotropic effects through the use of the reluctivity tensor in the two dimensional finite element formulation using the novel approach presented. As expected, a considerable improvement is obtained in the numerical results for the anisotropic case over the isotropic case as is vividly illustrated by the numerical and test results presented.

Recommended Citation

Isaac, Frederick Nicomedes, "A generalized anisotropic finite element formulation for the characterization of synchronous reluctance motor drives" (1998). Dissertations (1962 - 2010) Access via Proquest Digital Dissertations. AAI9901730.