On-board diagnostics method for detecting bearing defects in traction synchronous permanent magnet motors based on stator current spectrum

Introduction. The reliability of traction electric drive is a key factor determining the operational efficiency of urban electric transport. Bearing assemblies of electric motors remain one of the most common causes of failures leading to vehicle downtime.Materials and methods. A method has been developed for on-board diagnostics of rolling bearing defects in a traction synchronous motor with permanent magnets (SDM) based on the analysis of stator current spectrum (MCSA) with equivalent three-phase current used to normalize diagnostic features. In the study simulation modeling in the MATLAB/Simulink environment was carried out, covering the range of defect angular dimension from 0° to 8° and speeds from 1500 to 8000 rpm.Results. The method proposed sets clear limits to efficiency: the maximum speed for reliable defect detection is 5,000 rpm. At these and lower speeds in the stator current spectrum, a peak is observed of the mechanical rotor speed (fr), the amplitude of which correlates with the defect angular dimension. Normalization by equivalent operating current increases diagnostic accuracy.Discussion and conclusions. The proposed method makes it possible to implement an on-board diagnostic system without installing additional sensors, which is especially important for urban electric buses operating mainly in the range of 2000-5000 rpm. A new method has been developed that integrates normalization by equivalent operating current to quantify the diagnostic sensitivity of the analysis of the stator current spectrum depending on the rotor rotation speed in a permanent magnet synchronous motor and determines the critical speed threshold of 5000 rpm.