Laser additive manufacturing of soft magnetic cores for rotating electrical machinery: materials development and part designTools Garibaldi, Michele (2018) Laser additive manufacturing of soft magnetic cores for rotating electrical machinery: materials development and part design. PhD thesis, University of Nottingham.
AbstractThis research work addresses the application of Additive Manufacturing (AM) technologies in novel electrical machinery. The unrivalled design freedom offered by AM has the potential to revolutionise the way rotating electrical motors are designed and manufactured. The thesis investigates the possibility offered by AM to advance the design of electrical machines for lightweight and high performance, with potential in several industrial sectors, including automotive and aerospace. In particular, we investigate how the performance of electrical motors can be improved by manufacturing the soft magnetic rotor core using Selective Laser Melting (SLM) and how the consequent design choices affect the component’s performance from a torque-to-weight perspective. First, the metallurgical and soft magnetic properties of high-silicon steel (Fe-6.7%wt.Si) parts produced by Selective Laser Melting (SLM) will be characterised and discussed as function of the processing parameters and post-processing heat-treatments. The results of this research show that, by means of SLM, high-silicon steel parts with permeability (above 24000) and hysteresis loss (coercivity below 20 A/m) comparable to the ones of laminated high-silicon iron can be produced. Then, FEM-based modelling and Topology Optimisation (TO) will be employed to design the rotor core of a surface-mount Permanent Magnet (PM) machine in order to achieve maximum torque-to-weight ratio while maintaining structural integrity. Importantly, three-dimensional FEA results show that the weight of an existing PM rotor core can be slashed by 50% without affecting its torque performance when the proposed TO scheme is employed and the actual mechanical and magnetic properties of the SLM material are considered. Finally, we suggest that further research should be aimed at extending the range of applicability of the proposed TO scheme to other machine topologies (i.e., Synchronous Reluctance), as well as at the adjustment of the alloy’s chemistry for improved ductility to avoid the risk of in-process cracking.
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