Modelling considerations in the magnetic field analysis of rotating electrical machines using the finite element method

Most electrical machine design offices today employ the Finite Element Method (FEM) for the magnetic field analysis of electrical machines. The approach enables validation of design, comparative analysis of design options as also investigation of manufacturing outages and failure investigation. As compared to other areas of engineering, application of the method to the electrical regime is relatively recent and hence restricted to a handful practicing engineers in the country. However, this situation is changing fast with the arrival of user-friendly commercially vended FE software and high-powered desktop computers. A true mathematical representation in the FE environment can result only when the model, its material properties, excitations and boundary conditions are exactly representative of the physical phenomenon. The accuracy of FE results is known to be limited only by user-error introduced through incorrect modeling, inappropriate material properties and the like. While software user manuals detail features available in the software and their usage, published literature often avoid detailing the reasons underlying what is generally accepted as common practice. Therefore, there exists a strong need for propagating and documenting the considerations that underlie the right modeling practices. This paper presents an overview of the various criteria that dictate the modeling considerations and compares good analysis practices with gross approaches.