A Low Rotor Eddy Current Loss Design Approach to HSPMSM for Small-Scale Magnetically Suspended Turbomolecular Pump

Magnetically suspended turbomolecular pumps (MSTMPs) are key devices for achieving clean ultra-high vacuum (UHV). Due to their high speed, compact size, and significant levels of current harmonics, the rotor eddy current loss densities are substantial, resulting in excessive rotor temperature rises. In this article, a stator overhang structure is applied to the MSTMP motors to suppress the rotor eddy current loss. The focus is on proposing an optimization design method for stator-overhang motors (SOMs) that considers voltage constraints. This method is based on the analysis of the load and current characteristics of MSTMP motors. An equivalent 2-D analysis method that combines high computational accuracy and efficiency is proposed for parameter optimization specifically for the overhanging stator structure. The quantitative relationship between motor topology and current harmonics is established, with the winding inductance serving as the link. Based on this, the optimal SOM topology is obtained by the equivalent 2-D analysis model and the co-simulation of finite element analysis (FEA) and control system. As a result, the drive motor achieves the minimized rotor eddy current loss and maximized output torque. FEA result shows that the proposed method reduces the rotor eddy current loss by 86.6% under rated operating conditions compared to the traditional design method. Finally, two prototype machines are fabricated for experimental validation.