Today, centrifugal fans are used in a wide range of applications. Depending on where they are installed, resonances with increased vibration velocities may occur in unforeseen speed ranges. If the fan is often operated in such critical ranges, the drive motors’ bearing system may be damaged, leading to premature fan failure. Although these vibrations are measurable for the system operator, it is not easy to stop them. Automatic resonance detection provides a remedy. It avoids operation at critical speeds, which increases the service life and operational reliability of the fans»