Mechanical transmission and torsional vibration effects on induction machine stator current and torque in railway traction systems

In this paper, the mechanical transmission and torsional vibration effect on electrical machine torque and stator current in railway traction systems is investigated. Initially, a reduced scale (1/1275) experimental set-up of the traction part is developed and instrumented based on the extrapolation of real scale parameters. Previous studies on an elementary gearbox-based electromechanical system have shown how the transmission error, the different eccentricities of the pinion and the wheel, and the teeth contact stiffness variation, influence the electrical machine torque and stator current. In this way, it will be demonstrated that the electrical machine can be considered as a sensor by itself through the electromagnetic torque estimation for torsional vibration monitoring without any extra mechanical sensor. The results of the electromagnetic torque estimation are compared with the measured mechanical torque in steady-state condition to validate the proposed technique.