Influence of the supporting structure dynamic behaviour on the shaft vibration of a real rotating machine

Abstract

The dynamic behaviour of the supporting structure of rotating machines can significantly affect the shaft-train vibration. When a foundation natural frequency is close to the machine operating speed, the forces caused by even almost negligible malfunctions can cause very high vibration levels. This paper shows a case history in which a natural frequency of a generator case, and that of an auxiliary shaft, significantly affected the dynamic behaviour of a power unit. The existence of these critical natural frequencies has been confirmed through specific experimental tests, the results of which are shown in the paper.