Tech Tip: Analyzing electric signatures

Avoid “best guesses.”
PHOTO: THINKSTOCK

Electric signature analysis (ESA) should not require best guesses, but that may be called for when nameplates are missing.

There are methods and pattern recognition that, along with experience, can help; however, performing an analysis will take much longer and will be far less accurate as the amount of information decreases.

To get the greatest benefit out of an ESA, you’ll need complete nameplate, control and driven equipment information. For instance, if a motor is operating on a variable frequency drive (VFD) and drives a gearbox attached to a roll, you need information on the VFD, motor nameplate and gearbox nameplate (especially the ratio, or number of teeth of each gear, if available), and anything associated with the roll.

While bearing issues are difficult to detect, knowing the manufacturer, mode and other operating information will improve the chances for an accurate analysis.

For more information on ESA and analysis, review the related papers in the MotorDoc.com archives at www.motordoc.org/archives.

Source: Motor Diagnostics and Motor Health News, Success by Design, with permission.

This article appears in the Jan./Feb. 2015 issue of PLANT.