Multi-physics simulations for electrical machine development

In electrical machine R&D, like in other fields, different computation methods are needed for different purposes. For detailed analysis and product design, a multi-physical finite element (FEM) analysis is required. However, if advanced multi-objective optimisation of electromechanical devices is pursued, the computational burden of FEM analysis is too high, and more simple analytical models are needed. In this study, both alternatives are discussed. One hot topic in FEM computations has lately been the utilisation of open-source FEM tools. The benefits of open source can be found e.g. in massive parallel computation, more vast scripting possibilities, and possibility to tailor the software for special usage. Here, we study open-source FEM tools for three-dimensional (3D) electromagnetic and multi-physical simulation of electrical machines. The two most promising tools are Elmer and GetDP. We present two electrical machine test cases with Elmer. Elmer and GetDP are presently only opensource tools, which can solve 3D electromagnetic problems. However, they lack features needed for rotating electrical machine computations, e.g. they have limitations with the rotation model. The limitations are more severe in GetDP. The parallel performance of Elmer exceeds the results of GetDP, as GetDP utilises parallel computation only in linear solvers, whereas Elmer also in linear system assembly. Furthermore, in the test cases, Elmer shows a good parallel performance with rotating electrical machine models. Additionally, optimisation of electrical machines was studied. An analytical model implemented in MATLAB was used to represent an electrical machine in the optimisation process. Both single and multi-objective algorithms were tested in DAKOTA optimisation tool.