Variable speed drives (VSD) improve operation and performance of
pumping system and allowing them to operate efficiently, match
fluctuations in the water demand and hence saving energy over the
required range of field operation. Variation of speed may considerably
lead to coinciding of stationary speed with the critical speed. For VSD
applications, the excitation frequencies become variable and the likelihood
of encountering a resonance condition within the continuous operating
speed range is greatly increased. Vibration tests were done to obtain the
optimum Dynamic performance and its sensitivity due to speed variation.
The present work was done on a test rig of a centrifugal pump unit with a
variable speed drive. Forced vibration measurements were done at
different operating speed ranged from 25 Hz to 50 Hz to determine
vibration levels and exciting frequencies. Experimental modal testing was
done at different conditions to simulate the design and installation cases.
Operational modal analysis is done to simulate the actual operating
conditions. Dangerous frequencies are well determined to avoid operation
at resonance. Finite element model was done using ANSYS software to
obtain the dynamic characteristics of the pump model analytically.