Engineering Spectrum analysis of unbalanced rotating rotor

AI Thread Summary
The discussion focuses on the spectrum analysis of an unbalanced rotating rotor, comparing the acceleration spectrum against frequency for both balanced and unbalanced conditions. It notes that the shaft is driven by a 4-pole induction motor, which influences the fundamental frequency and slip rate. Participants inquire about the arrangement of unbalance screws on the disk, specifically the implications of having 2, 4, or 6 screws and their geometric positions. Understanding these configurations is crucial for analyzing the effects of unbalance on rotor dynamics. The conversation highlights the importance of precise measurement and arrangement in rotor performance analysis.
Tung Jian Seng
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Homework Statement
Hi guys, I have done a lab experiment about unbalanced rotating rotor.
In the first part of the experiment, the rotor was run in a balanced condition at different frequencies (40, 50 and 60 Hz). The spectrum of acceleration vs frequency for each frequency was recorded.
In the second part of the experiment, the rotor was run in unbalanced condition where screws are added on the rotor as the unbalanced mass. The results are recorded in 3 different frequencies (40, 50 and 60 Hz)

For the balanced case, I can observe that the acceleration decreases with the increasing frequency but I can't find the reason why does this happens?

For the unbalanced case, I can see that the acceleration increases with the increasing frequency. I would like to ask what does the increasing acceleration indicates?
And why do people choose to analyze the acceleration spectrum instead of velocity and displacement?
How does the acceleration can be related to vibration analysis?

These are my douts on this experiment. It would be much appreciated if anyone could help me out with this.

Thank you in advance.
Relevant Equations
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1646408577542.png


Spectrum of acceleration vs frequency
1646408742044.png


1646408769573.png
Results of balanced condition
1646408644888.png


Results of unbalanced condition
1646408677527.png
 
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I assume the shaft is driven by a 4 pole induction motor, which explains the rate of rotation, the fundamental frequency, and the small slip.

How many and how are the unbalance screws arranged in the disk?
What is meant by 2, 4 or 6 screws, in what geometric positions ?
 

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