3D thermal equivalent circuit model of a lightweight composite stator

Ambitious power density targets for future electric propulsion systems in air transport necessitate the development of novel electrical machine topologies. The slotless permanent magnet machine presents an opportunity to exploit high performance materials in lightweighting of electrical machines. However, a limiting feature of this topology is the exposure of the stator winding layer to the rotor reaction torque which would normally be borne by the mechanically robust stator teeth. To address this issue, a glass-fibre reinforced composite air-gap winding is developed. Since the performance of an electrical machine is thermally limited, an accurate prediction of machine power density relies upon a detailed thermal characterisation of the winding layer. Due to the complexity of the multimaterial amalgam, conventional empirical and analytical homogenisation approaches are insufficient and 3D Finite Element Analysis is too computationally costly if varying constituent materials are to be studied. Therefore, this paper proposes a parametric 3D thermal equivalent circuit model capable of evaluating the thermal behaviour of various arrangements of the composite stator winding layer. Reduced-scale representative composite winding samples are used to experimentally validate the thermal model via heat flow meter testing and evaluate the influence of manufacturing processes on effective thermal conductivity.