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

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Systems with variable frequency drives may experience torsional vibration. One reason is the pulsating nature of motor torque due to converter supply, another one is the electro-mechanical interaction and the effects of closed loop control. This paper deals with the speed control of elastic drive systems, mainly from torsional performance point of view. Modeling of elastic shaft string is being explored. The importance of control engineering to minimize the torsional vibration is explained. The paper also discusses different control strategies and their practical use in large resonant drive systems. Key factors in this part are complexity of the controller, its robustness and availability of required parameters. The practical aspects of the implementation in real control hardware are being considered. Attention is also paid to detection and monitoring of vibrations. Finally a verification method for correct parameterization on site is proposed. Different aspects are illustrated on simulations and calculations as well as on a real 6.1 MW compressor drive

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