First of all I see what may be 1X on the order of 10.44 um (red) vs. 8.35 um (green).  This could be perfectly normal and typical of a fluid film bearing.  The “oil wedge” formed in such a bearing supports the rotor and the result is usually an elliptically shaped orbit.  Thus the X vs. Y will result in differing values.  

Do you know why the 2X appears to be large as compared to the 1X?  Is this a 2-pole generator in which case it may be normal?  Do you have historical data that would indicate any changes occuring over time?

Dear Mr. John,

Appreciate your response.

How much variation between X&Y is not suspicious?

I exactly do not know why 2X is more than 1X. Kindly explain.

This is a 4 Pole generator tested at the factory before dispatch.

No historical data is available, because it is newly built.

Even though the levels are normal, I want to understand the reason so that it will help improve my way of thinking.

Dear Mr. John,

As mentioned in red color circles, why this signal is more at the low-frequency region, and why it is not seen for the remaining 2 plots?

Thank you

@Registered Member posted:

Dear Mr. John,

As mentioned in red color circles, why this signal is more at the low-frequency region, and why it is not seen for the remaining 2 plots?

Thank you

As you can see from the image I've attached I can't make out the two lowest spectra from your original post.  This isn't your problem, just one I encounter on this particular forum where the original post overlaps the forum header information.  Can you post the data as an Adobe attachment?  I would specifically be interested in knowing whether the data showing the 2X is the DE or NDE of the generator and also if the generator has a coupled exciter.

Dear Mr. John,

I understand the difficulty now, I better be posted in .pdf format. Anyways an experience in this forum. Please find the attached pdf file.

Your cursor is shown at 25 Hz (1250 cpm).  Was the generator synched at the time?  Can you expand the region from 0 Hz to about 100 Hz so we can get better definition of the frequencies that are shown?  I'm interested in knowing if that DE is showing 1X and 2X and the NDE only showing 1X.  Also, what type of coupling is at the DE of the generator?