motor vibrations

[benmoulai]

hello
i want to explain this readings,new electric motor installed recorded high vibration an acceleration mesurements of two bearings,running speed is 1480 rpm,150kw.
the spectrums shows the slot frequency at high amplitude.the motor coupled with centrifuge pump.what you think.
thanks

 

[electricpete]

I assume what you are seeing is rotor bar pass frequency. High rotor bar pass frequency is very common, even in good motors. Uusally it consists of multiple sidebands spaced at twice line frequency around rotor bar pass frequency

I believe the rbpf pattern doesn't have much diagnostic value by itself. . It may be inherent in the design of the motor, and it may be aggravated by soft foor or misalignment. Soft foot can be checked on-line by loosening only 1 foot at a time to see if the vib goes away.

On rare occasions strange patterns in RBPF and stator slot pass may indicate something more sinsiter. Look at the lower frequency stuff for more info. 2*Line frequency, possible pole pass sidebands around 1x.