文档介绍：Predictive maintenance tips for electric motors
Vibration monitoring, electrical testing and visual inspections can help keep electrical motors
humming along
Electric motors are the mon source of motive power for machine trains. An effective predictive
maintenance (PdM) program for them must include bination of vibration monitoring, electrical
testing and visual inspections.
Vibration monitoring
The vibration frequencies of the following parameters are monitored to evaluate operating condition. This
information is used to establish a database.
Bearing frequencies.
Electric motors use either sleeve or rolling-element bearings. Establish a narrowband window to monitor
both normal rotational and defect frequencies associated with each bearing type.
Imbalance. Electric motors are susceptible to a variety of forcing functions that cause instability or
imbalance. While the narrowbands are useful in identifying mechanical imbalance, other indices also
should be used.
One such index is line frequency, which provides indications of instability. Modulations, or harmonics, of
line frequency may indicate the motor's inability to find and hold ic center. In-line frequency
variations also increase the amplitude of the fundamental and other harmonics of running speed.
Axial movement and the resulting presence of a third harmonic of the