Motor bearing damage detection using stator current monitoring

TLDR

Vibration monitoring of mechanical bearing frequencies is used to detect faults, and because these vibrations alter the air‑gap flux density, they modulate stator currents at predictable frequencies related to both the supply and the bearing’s characteristic vibration frequencies. The study investigates whether motor current spectral analysis can detect rolling‑element bearing damage in induction machines by correlating vibration‑induced current frequency changes with incipient bearing failures. The authors analyze the stator current spectrum of induction machines, identify frequencies linked to bearing vibration, and validate the correlation with experimental vibration and current spectra from machines with various bearing faults. The results demonstrate that stator current signatures can reliably identify bearing faults, supporting the development of a current‑based fault detection scheme.

Abstract

This paper addresses the application of motor current spectral analysis for the detection of rolling-element bearing damage in induction machines. Vibration monitoring of mechanical bearing frequencies is currently used to detect the presence of a fault condition. Since these mechanical vibrations are associated with variations in the physical air gap of the machine, the air gap flux density is modulated and stator currents are generated at predictable frequencies related to the electrical supply and vibrational frequencies. This paper takes the initial step of investigating the efficacy of current monitoring for bearing fault detection by correlating the relationship between vibration and current frequencies caused by incipient bearing failures. The bearing failure modes are reviewed and the characteristic bearing frequencies associated with the physical construction of the bearings are defined. The effects on the stator current spectrum are described and the related frequencies determined. This is an important result in the formulation of a fault detection scheme that monitors the stator currents. Experimental results which show the vibration and current spectra of an induction machine with different bearing faults are used to verify the relationship between the vibrational and current frequencies. The test results clearly illustrate that the stator current signature can be used to identify the presence of a bearing fault.