Generation of torsional excitation in a variable-speed-drive system

Torsional vibration issues in elastic drive systems are a well-known topic both in the research area and in the industrial field. A considerable number of papers appear over the last two decades discussing the source of torque and speed ripple in variable speed drive (VSD) technologies and their connection with the mechanical characteristics as the torsional natural frequencies (TNFs). This paper provides a detailed description of the potential mechanical failures in a system equipped with a VSD and it explains which are the sources of torsional excitations focusing on the interactions between electrical side and mechanical side. The effects on the coupling torque of the so called critical speeds will be investigated with both the Campbell diagram and the Waterfall diagram tools in order to predict some potential failures in the drive-shaft