spectrum for AC motor 200KW?

[alexsurf]

hello all,

I wish you all an HAPPY NEW YEAR

I made one radial measurment on a motor and i found
in velocity spectrum 2 pics : 21,3Hz;4mm/s and 24,9Hz;4mm/s
and
in demodulated spectrum pics: 100,5Hz with 3 harmonics and 941Hz with side bands of 100,5Hz

What could we say ?

THANK YOU

 

[electricpete]

What is the motor speed?

I tend to think your demod stuff is not a concern (although we usually don't go that high on demod spectrum).

Would be interested to determine whether your two velocity frequencies are non-sync or sidebands around a running speed.

Is it only shaking on one direction (h) or both (h and v)?
Is there axial vibration?

 

[alexsurf]

i have only take a vertical radial measurment

at the end of the motor, there is an hydraulic coupling

As you said, i have to look only on the velocity spectrum.

-So you think that i have to take horizontal radial measurment and axial ?

-but with this data, do you think something looks good or bad in this motor ?

 

[electricpete]

Good or bad? I would say the magnitude is normally one that should prompt additional investigation. (don't ignore it).

Of even more concern, the frequencies are not yet understood. We need to know the motor speed to help judge the significance of those frequencies. Unless this is a variable speed machine I would have to think those are non-syncronous frequencies frequently associated with rolling bearing defect. Do you have information on the types of bearings?

Two radial measurements 90 degrees apart would be helpful. Often times vertical machines have resonant vibration and it shows up in only one orientation.

 

[electricpete]

Also if info is available it is always helpful to know the horsepower of the machine, what is it driving, any special coupling, is it new or old, did vib change etc.

 

[alexsurf]

motor speed is about 25Hz

 

[alexsurf]

ISO value 10-1000Hz in vertical radial position: is back:4,5mm/s and front:5,1mm/s

ISO limit is 11,2mm/s ?

but constructor tell 3,5mm/s ? (what does it mean, motor only without coupling ? or maximum limit with coupling ?)