Copper vs. aluminium winding SRMs: a multidisciplinary performance assessment

The winding represents an essential element in every electrical machine. Winding design and operating conditions have a direct influence - among others - on torque performance, thermal behaviour, voltage stress distribution and ensuing machine reliability and lifetime. With reference to switched reluctance machines, the winding represents the sole `source of excitation', implying that any modification (e.g., in terms of layout, materials or operating conditions) can strongly affect the capability of delivering shaft torque in a satisfactory manner. Accordingly, this paper aims at investigating, through a multidisciplinary approach, how shifting from copper to aluminium winding can affect the performance of switched reluctance machines. By relying on a purposely designed use-case machine, it is found that in some contexts (or applications) the use of aluminium could provide a higher peak power density, although with a lower thermal margin. Furthermore, it is demonstrated that in an aluminium-winding switched reluctance machine, stator modes of vibration are excited at slightly higher frequencies, potentially leading to a reduction in emitted acoustic noise.