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.