Use of residual stress based flux barriers to increase the power density of rotating electrical machines

• Applicants: Dr.-Ing. Nora Leuning; Dr. Michael Schulz; Professor Dr.-Ing. Wolfram Volk
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 532773068

In the applied project, the application of the previous project phases of the priority program is in the focus of the scientific activity. Together with the project partner MUBEA, both the practicability of residual stress-based magnetic flux barriers and their integration into the manufacturing process of laminations of electrical machines and the actual improvement in properties due to higher speeds and increased energy densities of the electric motors are to be demonstrated. The basic idea of the project is to selectively introduce local residual stresses into the sheet cross-section of rotors whose operation is based on strong magnetic anisotropy (PMSM and SynRM), thus ensuring wider remaining bridges and higher mechanical stability while maintaining magnetic anisotropy. Due to the increased mechanical stability, higher rotational speeds of the drives could thus be realized, resulting in increased power density. At the beginning of the project, one of the two anisotropy-based machine topologies will be selected in close consultation with MUBEA. On the basis of this electrical machine topology, the process and the property improvement will be demonstrated. Following the decision, a series machine that meets the current standard of traction drives in electromobility will be procured. The boundary conditions such as the axial length and the outer and inner diameters are specified. In the following steps of the project, analytical considerations as well as finite element simulations are used to create an alternative innovation rotor geometry that is compatible with the procured motor component but has a different cutting geometry. For this purpose, a detailed material characterization with respect to magneto-mechanical coupling as well as mechanical strength is performed. In order to avoid possible distortions of the comparison of series and innovation rotor due to different electrical steel strip and joining and separating processes deviating from series production, a reference rotor will be built that has an identical magnetic cross-section to the series machine but is manufactured from the material selected for the project and under the same manufacturing processes as the innovation rotor. The prototype construction and the exact process steps will be determined in close coordination with the industrial cooperation partner MUBEA. Following the construction of the reference and innovation rotor, the different rotors will be measured in operation to determine the efficiency and the generated torque under identical energization at different speeds. In addition, the final work package will use centrifugal tests and electromagnetic and mechanical simulations to determine the increase in energy density due to the increased mechanical strength and thus the increase in the maximum possible speed.

• DFG Programme: Research Grants (Transfer Project)
• Application Partner: Muhr und Bender KG