Vibration analysis requires a correct identification of the rotational speed of the machine. How the different frequencies of the spectrum are related to RPM, identifying with high accuracy the order of each frequency, is essential for the analysis process.
Variable frequency drives (VFDs) have become a preferred method of process control for electric motor driven equipment ranging from vertical water pumps to centrifugal air fans. The following is a basic discussion of risks of using a VFD with direct driven centrifugal fans and methods of mitigating those risks to maintain equipment reliability.
- David Sheffler
- IVC Technologies
The simulator of measuring system (Lead Phase or Lag Phase), phase convention (Rotating Scale or Fixed Scale) and scale direction (Contrary to Rotation or Same of Rotation), shows, during rotation, for the first turn the tachometer event...
- Jose Mendez Adriani
- Central University of Venezuela
There are a lot of equipment types in industry that exhibit continuously varying speed. This presents a number of challenges to the vibration analyst. If a time sample is collected as the machine is continuously changing speed, the FFT will produce a virtually useless plot...
- Greg Lee