Additive Manufacturing of electric machines: Research on the potential of additivemanufacturing of PM synchronous machine rotors

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Additive manufacturing processes produce components and assemblies layer by layer without using formative tools. This process generates additional and new degrees of freedom in designing the geometry of the components as well as in designing the material properties. The focus of this research project is to use these new degrees of freedom for improving the design and manufacturing of electrical machines, especially of rotors of permanent magnet excited synchronous machines (PMSM). In previous research, fundamental knowledge on different material systems for AM, their characterization and their application in electrical machines were achieved in tight cooperation between the University of Paderborn's Direct Manufacturing Research Center (DMRC) and the Institute for Drive Systems and Power Electronics (IAL) of Leibniz Universität Hannover. The research project proposed here addresses the fields 'material research for AM', 'rotor design', 'rotor manufacturing' and 'rotor test'. On the field of material research, suitable soft magnetic materials for electrical machines and the respective process parameters for AM are identified by means of systematic parameter studies. The focus lies on one FeCo and two FeSi alloys. In order to characterize these materials, their electrical, magnetic and structural mechanic properties shall be determined on AM test specimen. These results shall be used in the second phase of the project for designing rotors of PMSM. The identified material properties and the new degrees of freedom in design due to AM shall be used to improve the manufacturability and the technical parameters of PMSM, e.g. by rotor skewing without increasing the PM leakage flux and by reducing eddy currents on the rotor surface with a special surface shaping. For these new AM rotor concepts, design rules are required for both, electromagnetical and mechanical design. These shall be elaborated in order to care for robust design and easy manufacturability.In the third phase of the project, prototype rotors shall be manufactured by AM and, if required, mechanical or thermal postprocessing. Finally, these rotors will be evaluated by experiment in order to validate the predicted electromagnetical and mechanical properties and operational behaviour, e.g. torque density, efficiency, and torsional strength. In order to demonstrate the benefits of AM for electrical machine manufacturing, comparisons shall be made to conventionally manufactured rotors by simulation as well as by measurement.