Mechanical failures detection by means of induction machine current analysis: A case history

This paper addresses the problem of the detection of the mechanical disturbances and failures in a mechanical system driven by asynchronous machines through motor's current signal. Since the load behavior modifies the motor's supply current, it is possible to use the machine itself through motor current signal analysis (MCSA), as a torque sensor to defect mechanical condition. In this paper low frequency torque disturbances, that cause a quasi-stationary machine-load behaviour are used to diagnose the different mechanical anomalies, exploiting the relationship between current and torque. Specifically a mechanical system constituted by a high-ratio gear and a grinding table with rolling wheels for raw coal was analyzed through MCSA.