Multiphysics Optimisation of a Slotless Permanent Magnet Machine with a Composite Winding Layer

Ambitious power density targets for future electric propulsion systems in air transport necessitate the development of novel electrical machine topologies. The Slot-Less Permanent Magnet machine (SLPM) topology presents a substantial weight reduction and opportunity to exploit innovative winding designs and high performance materials. However, a limiting feature of SLPM machines is the exposure of the stator winding layer to the rotor reaction torque which would normally be borne by the mechanically strong stator teeth. To address this issue, an SLPM machine with a glass fibre composite winding layer has been developed and the specific output benefits of using a skewed winding with no end overhang is assessed. An analytical multiphysics design procedure and optimisation routine is presented to maximise the mass power density (kW/kg) of an SLPM composite machine with the design benchmarked against a conventional slotted permanent magnet machine to highlight the volume and mass benefits of the SLPM topology.