Towards Multi-physics Optimisation of Electrical Machine Housings

The demand for higher efficiency and reduced weight in electric machines has driven designers to explore advanced materials and innovative assembly techniques. One such method is shrink-fitting, which offers advantages over traditional mechanical joints such as keyways, particularly in reducing overall weight and complexity whilst maintaining sufficient holding torque or axial resistance to load through friction. In electric machines, shrink-fitting can be applied between the motor housing and the stator to provide a structurally integral assembly. This method also enhances thermal conductivity and heat dissipation though the increased stress on the stator can interduce higher iron losses. This paper investigates the mechanical effect of the shrink-fit process on stator materials, with a focus on understanding the frictional holding torque as first stage in the overall optimisation of shrink-fit of stators in electric machine housing. Several physical parameters are experimentally examined, including material properties, surface topography, coefficient of friction at the interface under various pressure, and the effects of manufacturing processes such as wire EDM, grinding and punching.