Torsional-Vibration Assessment and Gear-Fault Diagnosis in Railway Traction System

The diagnosis of mechanical faults in railway traction systems (RTSs) has a significant importance on both safety and reliability, which can avoid train crashes. This paper deals with torsional-vibration assessment and gear-fault diagnosis in the mechanical transmission of a high-speed RTS by a fully noninvasive technique. Previous studies on a simple gearbox-based electromechanical system have shown that the influence of gearbox torsional vibrations on the torque and on the stator-current signatures are obvious. The aim of this paper is to demonstrate that the traction motor can be considered as a torque sensor through its electromagnetic-torque estimation for torsional-vibration monitoring without any extra mechanical sensor. The effects of both tooth-damage and surface-wear faults at the output wheel on the stator current and on the estimated electromagnetic torque have been investigated. The results of the estimation are compared with the measured mechanical torque and validated through a reduced-scale RTS in both stationary and nonstationary conditions.