Sign up Calendar Latest Topics Donate
 
 
 


Reply
  Author   Comment  
ram

Member
Registered:
Posts: 27
Reply with quote  #1 
There are 2 spectrums of different 4 pole induction motors to drive reciprocating compressor. Can anyone tell the peak and it's sidebands

 
Attached Files
doc j-101 c.doc (81.50 KB, 81 views)

Walt Strong

Sr. Member
Registered:
Posts: 889
Reply with quote  #2 
The information is there, but scattered all over the plot! What software is this, since I would avoid it?

Walt
John from PA

Sr. Member
Registered:
Posts: 963
Reply with quote  #3 
Excellent reference on induction motor diagnostics at https://www.industry.usa.siemens.com/drives/us/en/electric-motor/anema-motors/specification/documents/approach-to-solving-motor-vibration-prob.pdf.

I would look specifically at the section, page 4, titled "Rotor Bar Passing Frequency Vibration:".
ram

Member
Registered:
Posts: 27
Reply with quote  #4 
E-monitor
Walt Strong

Sr. Member
Registered:
Posts: 889
Reply with quote  #5 
RAM,

What kind of an answer are you expecting without providing any machine information? You show two machines (CO2 and Syngas compressors) with one measured horizontally and one measured vertically. You are not even comparing spectra with the same F-max frequency. My calculator indicates dominant peak in 1st plot is 56xSS and 44xSS in second plot. The sideband frequencies in 1st plot are spaced at ~487 cpm, so is compressor driven by belt or gear drive? 

Walt
ram

Member
Registered:
Posts: 27
Reply with quote  #6 
Both are belt drive.my intention is to know the prominence of sidebands.thease are close to compressor RPM.what indicates the motor spectrum at higher frequency probably rotor bar frequency with compressor rpm sidebands.
Curran919

Avatar / Picture

Sr. Member / Supporter
Registered:
Posts: 599
Reply with quote  #7 
Quote:
Originally Posted by John from PA
Excellent reference on induction motor diagnostics at https://www.industry.usa.siemens.com/drives/us/en/electric-motor/anema-motors/specification/documents/approach-to-solving-motor-vibration-prob.pdf.

I would look specifically at the section, page 4, titled "Rotor Bar Passing Frequency Vibration:".


Thanks John. Started going through that today. As the pump guys, we always treat the motor like a blackbox that ABB/GE/Toshiba/Baldor don't want you meddling with, but this helps demystify that side. Its funny though, how they start with complex topics like 'elliptical stator due to fundamental flux' and end with the real fundamentals such as the DVA relationship and equations of motion.
electricpete

Sr. Member
Registered:
Posts: 651
Reply with quote  #8 

If you're sure these sidebands in motor vibration are compressor speed (or even multiples of compressor speed), I would think about torsional oscillation excited by recip torque pulsations.  Just a thought.

ram

Member
Registered:
Posts: 27
Reply with quote  #9 
Thank u for reply.if it is torsional vibration is it only seen at higher rpm
Ralph Stewart

Avatar / Picture

Sr. Member
Registered:
Posts: 235
Reply with quote  #10 
Ram's Quote:
Quote:
if it is torsional vibration is it only seen at higher rpm?


In my opinion,:::
If the sidebands are truly the compressor speed, and if the "high frequency" carrier, and its harmonics, are slotpass frequencies or rotor bar pass frequencies, then the motor is responding to the impulses or torsional vibration from the compressor, in the same manner the motor would be responding to something else which causes sidebands on slotpass frequency or rotor bar pass frequency, such as:::: line frequency, 2x line frequency, 1x motor speed, belt speed, and/or any other thing that affects the motor's rotational operation.

Only my opinion and I could be totally wrong. [smile]

Thanks and Have a Great Day,
Ralph


__________________
Ralph Stewart
AlertAnalytical.com
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.