Comparison of winding concepts for bearingless pumps

Bearingless slice motors as employed in semiconductor, pharmaceutical and medical industry perform magnetic levitation by radial bearing forces and rotation by tangential forces. This requires bearing and drive windings, which can be realized as separate bearing and drive coils or as identical, concentrated coils on the stator claws. In this paper, a detailed comparison between these two winding concepts is undertaken, where the coil losses, the coil volume, the power electronics requirements and the achievable rotation speed are evaluated. Furthermore, practical features such as control complexity, cabling effort and manufacturability are taken into account. Finally, the trade-off between losses, volume and realization effort will be discussed in order to give a guideline for the selection of the appropriate winding concept for a specific application of a bearingless pump.