Detecting a Hidden Lateral Rotor Natural Frequency in a Sewage Pump
by: Paul Boyadjis
June 2004

The need for municipalities to save money and control energy costs is a driving force in the decision by many of them to implement the use of Variable Frequency Drives (VFDs) in their operations. Yet, while VFDs clearly offer versatility to the pumping industry and cost savings to the consumer, they also present some difficult engineering challenges for both suppliers and users - particularly in the area of vibration.

In countless municipalities across the country, VFDs adjust motor speeds driving pumps to match fluctuations in flow rate demand that arise from a community’s daily and nightly sewage usage. A given sewage pump can and does run over a wide range of speeds to match these fluctuations. This, in turn, vastly increases the chances of exciting a natural frequency in the system from a variety of sources, such as 1x imbalance and vane pass that otherwise may not have been excited by a constant speed driver...

This technical article appeared in the June 2004 edition of PUMPS & SYSTEMS magazine.

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