Can someone explain the plots in "Figure 3" on page "47" in the article about "The Energy Efficiency Myth"?

Hey Ralph

What issue was that in??

Lee,

September 2006

Sorry...... I put it in the "title" of the thread but guess I should have put it in the lead off post too. Sorry Again.

Article in "UPTIME" Magazine September 2006

Ralph:

I am the author, also took the data and performed the analysis. What are you interested in knowing?

Howard

Thanks Howard,

Sorry I did not associate the author name to you, I think of you as MotorDoc.

The circle drawn around the "peaks" in the lower plot, which are circled and labeled [b]"Excessive fan signature peaks indicating alignment and tensioning problems. Correct immediately."[/]

I see the lower plot is a demodulation spectrum displayed in Db. What is it's relation or comparision to the current plot above it, where the "arrows" are pointing to 4 peaks which do not appear equally spaced from the LF peak. That is, not equally spaced to each other as far as being the same distance from LF.The first left and right seem to match and the second left and right seem to match, but not first to second. What do these "sidebands" of LF represent, tension and misalignment?

How can I determine from this circled area and the above current plot, that there is too much misalignment and tensioning problems to continue to run safely?

Maybe I missed something in the wording within the article.

Ralph:

Pardon the delay, I was completing some travel and an urgent business matter.

When you demodulate the low frequency current spectrum, you, in effect, can fold the modulated frequency on top of itself at the line frequency. The demodulated spectra has the line frequency dB level removed, which allows lower value peaks to show, with the highest peak showing as 0dB.

So, first thing is that the fan and belt signatures show in the demodulated spectra. This identifies that they exist. The exact same signatures are mirrored on either side of the line frequency, which provides me information on the severity of the problem.

In this case, the situation was very serious and confirmed once the machine was shut down and it was discovered that the belts were not aligned and were arbitrarily tightened until there was no sag or flap while it was running (no belt tensioning device was used and the belts were extremely tight).

Unfortunately, given the time to develop the article (one day plus one day for approval via the client), I was unable to expand on much. I will return to the subject in Uptime at a later date, as well as the energy efficiency topic, which also generated a few direct emails.

Sincerely,
Howard