Torsional Vibrations in Turbogenerators Due to Network Disturbances

Abstract

Large steam-turbine generators in operation may be stimulated to torsional vibrations by dynamic moments at the generator due to electrical system transients. The induced torsional stresses in the shaft have drawn growing attention over the past few years. To solve the torsional vibration problem the turbogenerator shaft is modelled by the finite element method. This paper presents the results for a 600 MW turbogenerator set. To verify the quality of the used finite element model measurements were carried out and compared with the analytical results. For some applications it is desirable to have a torsional model with a reduced number of degrees of freedom, which reproduces the finite element model only in the lower eigenfrequencies and modes. This paper describes a method on how to find the most accurate reduced torsional model with discrete masses and springs from the finite element model.

Torsional Vibration Analysis of Gear-Branched Systems by Finite Element Method

“…This is the reason why the coe$cients of "rst row and "rst column in the elemental mass matrices [m C ] and [m C ] are all equal to zero, as one may see from equation (14).…”

“…given by equation (14). From Figure 2(c), one sees that disk 3 is connected with shafts (2) and (3), while disk 4 is connected with shafts (3) and (4).…”

“…In recent years, the "nite element method (FEM) has been used to do the torsional vibration analysis of a straight-geared system [14] and a gear-branched system [15,16]. In general, the FEM formulation for a gear-branched system is much di$cult than that of a straight-geared system.…”

Torsional damping of a back-to-back gearbox rig: Experimental measurements and frequency domain modelling

“…Of particular interest are measurements of torsional natural frequencies, operating de ected shapes and modal damping levels for machines with electrical drives and gearboxes. Many problems are related to torsional resonance or instability [1][2][3]. Torsional natural frequencies can usually be determined with acceptable accuracy, but accurate measurements of torsional damping levels are generally more dif cult.…”