Numerical Study of Motor Electrical Signature for Condition Monitoring of Gear Tooth Breakage in a Motor-Gear System

Gearboxes are the most significant components of an electromechanical system. They are often exposed to various abnormal working condition which causes damage to the gear. These damages can be of any form such as tooth breakage, tooth wear. Furthermore, this breakage will cause changes in gear tooth mesh stiffness, thereby reducing the gear dynamics. Recently, several attempts have been performed for the detection of localized gear tooth faults using electric signatures from induction motor with promising results. However, the interaction between the motor-gear dynamics to detect and diagnose this fault has not been fully investigated. Therefore, this study proposed a 6° of freedom (DOF) electrical motor model integrated with an 18° of freedom (DOF) gear dynamic model to fulfil the detection of gear faults using motor current signature. In this model, a comparison of electric torque and constant torque as the input for the gear model has been investigated to study the influence of electric motor torque on gear dynamic. Furthermore, this study considered different severities of tooth breakage to demonstrate the performance of motor current in gear tooth breakage detection and its location. The numerical results show an increase in amplitudes at the frequency of ƒ_sƒ_r1 and ƒ_sƒ_r2 as the severity of the fault increases at different stage of the gearbox which can reflect the presence of tooth breakage. This proposed numerical analysis does have a good agreement with the experimental validation.