A Novel Design of Modular Bearingless PMSM Motor for Ultra Clean Applications

This paper introduces a novel design for achieving bearingless operation in a modular PMSM motor, specifically used for ultra-cleanroom applications in semiconductor wafer production. In order to achieve this operation, a stable and independent suspension of the rotor is crucial, which can be obtained through precise decoupling between the electromagnetic torque of the motor and the radial suspension force of the magnetic bearing assembly. To ensure this decoupling in the proposed machine, the stator of the motor part is isolated and distinct from the suspension winding poles named a suspension stator while the motoring rotor lies on the suspension rotor via an isolated material. Therefore, the independent placement of suspension force and torque assemblies ensures that the generated suspension force exhibits exceptional linearity concerning the rotor position and remains unaffected by variations in the torque current. This makes the suspension force more controllable for the levitation of the rotor assemblies in the air gap. To validate the effectiveness of this design, a mathematical model for the suspension force is established and analyzed through 3D finite element analysis (FEM). At the same time, the motor’s performance is investigated through 2D FEM. In addition, the control of the suspension assembly is conducted using Model Predictive Control (MPC) in MATLAB/Simulink. Finally, the influence of structural parameters on torque and suspension assemblies is analyzed in terms of decoupling characteristics using combined analysis via 3D FEM.