Reduced-order shaft system models of turbogenerators

Two very simple, sufficiently accurate reduced-order shaft system models, the truncated modal model and the aggregated mass model, used in turbogenerator torsional oscillation analysis are presented. The first is developed by taking the exact duplicate of the transient behavior of the original as far as the low-order modes are concerned, while the second is established by fitting the low-order mode shapes of the original. They can be implemented into existing programs without any difficulty, while the fidelity can easily be adjusted by changing their orders.>