Fatigue life expenditure assessment and countermeasure for turbine blades due to harmonic excitations of slip energy recovery drives

The long-term effect of noncharacteristic harmonic currents arising from a slip energy recovery drive (SERD) on the fatigue life expenditure in turbine-generator blades is presented in this paper. Since the SERD converter can be rated at a fraction of a motor due to its static converter cascade with the wound-rotor and with high efficiency characteristics, still the feedwater pumps (FPs) in a few power plants are driven by Such an induction motor (IM) drive. However, because the frequencies of the three main harmonic terms of the recovery currents are subsynchronous and offer a probability distribution due to the adjustable speed operation, a systematic Fatigue estimation approach was devised by the author to investigate the long-term impact for the low-pressure (LP) turbine blades. From the simulation results, it was found that Such a long-term harmonic excitation becomes a cause of turbine blade failure for single generator connected to the SERD system, even though the amplitude of these harmonic currents is normal. By the effect analysis of uncertainty, the countermeasure for the turbine integrity was then found. Copyright (C) 2008 John Wiley & Sons, Ltd.