Drivetrain Gearbox Fault Diagnosis: Vibration- and Current-Based Approaches

Gearboxes are widely used in rotary machines, such as wind turbines, automobiles, and helicopters. Gearbox failures contribute to a significant proportion of the total failures and downtime in these machines. Gearbox fault diagnosis is an effective means to prevent catastrophic failures, improve reliability, and reduce downtime and maintenance costs. Vibration-based approaches have been employed in most commercially available condition-monitoring systems (CMS s), while current-based approaches have received increased attention in industry and academia. This article presents a comparative study of vibration- and current-based approaches for gearbox fault diagnosis. Theoretical analysis and experimental tests are conducted to show that 1) in vibration signals, ghost frequencies appear when the gearbox is healthy and disappear when a localized gear fault occurs; 2) vibration signals of a faulty gearbox are modulated by shaft rotating frequencies; 3) in current signals, the fundamental frequency component is dominant; and 4) they are modulated by gearbox characteristic frequencies at the fundamental frequency when gear faults appear.