Journals Proceedings

Abstract

To improve turbogenerator (TG) rotor design,Torsional vibration analysis is necessary. Torsional vibration of turbogenerator shaft occurs due to the electrical unbalances and disturbances in the generator (short circuits, line switching, faulty synchronizing etc). In the present paper 3-Dimensional (3D) solid finite element (FE) is used in FE software ANSYS, to evaluate the natural frequencies and dynamic response due to transient torque excitations. The 3D solid model eliminates the assumption inherent in the 1-Dimensioanl (1D) model, and therefore provides more realistic results. The simulation of transient torque disturbances on the rotor system caused by different short circuit faults has been performed on 3D model and the response is obtained. The computational time required for the analysis by 3D solid model is relatively more. However the 3D solid FE model provides information about all modes including the shaft and disc coupling effect. The response calculated through analytical method, is also presented. The alternating shear stress values obtained due to three phase short circuit fault are found to be more compared to stresses obtained due to line to line, and line ground short circuit fault. It is concluded that 3D modeling using solid finite elements gives more realistic and complete results, and thereby provides a superior TG design capability.