Installing VFD Drives On Vertical Pumps and Structural Vibration Problems

By: Nelson Baxter It is well known that the installation of VFD drives has the possibility of introducing vibration problems on rotating equipment.  When a machine runs through a wide speed range the probability of operating at or near a resonance is significantly increased as compared to a machine operating at a single frequency. VFDs are generally utilized to slow the speed of a machine down to match the load, thus saving energy and allowing better control of the process.  The inherent nature of the design of vertical pumps means that there is a large mass (the motor) sitting on top [...]