Electrical Motor Vibration Root Cause Failure Analysis using Signal Processing: A Case Study

Bearings are vital parts of machines that tolerate load and guide rotors to rotate axially the most accurately possible. Bearing assembly is very important for convenient vibration behavior and increasing useful life. In this research, the main probable root cause of mechanical vibration of the electric motor is explained. Three bearings are analyzed. The first bearing has been changed because of bearing failure due to frequency excitation and vibration amplitude. On the first time running the replacement bearing (second analyzed bearing), the vibration, under the unloaded situation, was higher than normal without getting any failure signals excitation. Based on vibration analysis and signal processing, the vibration peak was at 1 x rpm in non-drive end (NDE) of the motor which may let us think about a bad bearing assembly. Inadequate preload conditions, bearing seat, or housing looseness may cause this abnormal vibration amplitude. This paper uses mechanical symptoms and vibration signals to explain the main probable root cause of vibration amplitude. Relative movement based on unadopted fits or axial preload is one of the main causes of the bearing outer ring fretting corrosion. Fretting corrosion and vibration amplitude result from improper fits and bad mounting conditions. This work explains how to interpret vibration signals coming from fretting corrosion.