Estimating turbogenerator foundation parameters

Turbogenerators in power stations are often placed on foundation structures that are flexible over the running range of the machine and can therefore contribute to its dynamics. Established methods of obtaining structural mod els for these foundations, such as the finite element method or modal testi ng, have proved unsuccessful because of complexity or cost. Another method of foundation system identification, using the unbalance excitation applied by the rotor itself during maintenance run-downs, has previously been prop osed but has not yet been experimentally verified. In this paper the necess ary theory is developed and certain issues critical to the success of the e stimation are examined. The method is tested in both simulation and experim ent using a two-bearing rotor rig and good fits between model and measureme nt are obtained. The predictive capacity of the estimated models when the s ystem is excited with a different unbalance is not as good, and it is surmi sed that this may be due among other things to inaccurate bearing models.