Vibration analysis of the propulsion shaft system caused by motor manufacturing imperfections based on electromechanical dynamic model

Manufacturing tolerances are inevitably introduced into the permanent magnet synchronous motor due to stamping die precision and process-related die wear. Revealing the mechanism of the typical stator and rotor core manufacturing imperfections on electromechanical vibration characteristics can provide references for the selection of manufacturing tolerances, thereby enabling the design of a propulsion shaft system permanent magnet synchronous motor with lower vibration and processing costs. Therefore, a developed electromechanical coupling dynamic model of the propulsion shaft system considering permanent magnet synchronous motor manufacturing tolerances is proposed. The current vector control, the permanent magnet synchronous motor magnetic equivalent circuit model, and the flexible rotor-bearing subsystems of the coupling model are comprehensively included, and interaction relationships among these subparts are fully demonstrated. The shape function method utilized in the traditional magnetic equivalent circuit model is developed to precisely quantify the air gap permanence under rotor displacements, and the correctness of the coupling model is verified by the finite element method and the experiment. Based on the proposed coupling model, the effectiveness of five kinds of stator and rotor manufacturing imperfections on the time–frequency characteristics of the electromagnetic excitations and propulsion shaft system vibration is studied. The manufacturing tolerance selection interval of the permanent magnet synchronous motor in this study is given, and the spectral characteristics of each imperfection are obtained, which can provide theoretical guidance for the diagnosis of permanent magnet synchronous motor manufacturing imperfections.