Optimization of transient behavior of complex turbocompressor shaft lines

A considerable number of papers appeared over the last two decades discussing the origin of torque ripple for the different variable speed drive technologies. Direct reaction of mechanical loads to this excitation was investigated deeply. However only recently, it was recognized that the drives and the mechanical shaft line form a closed-loop control system, and that - as they are interacting with each other both ways - the resulting torsional behavior may be quite different from the traditional considerations in feed forward from drive to shaft line. This paper shows how closed loop effects can take place, leading to momentary, unexpected high alternating torque, which could impact the shaft line integrity. It then focuses on the optimization of transient behavior in order to avoid potentially adverse interactions between converter control system and train dynamics.