Finite element modelling of turbine generator stator end windings for vibration analysis

In this study, the authors present methods for accurately modelling the bindings and the stator bars of turbine generator stator end windings for vibration analyses. The bindings are modelled with beam elements and multipoint constraint equations to take account of the bending, twisting, and shearing rigidities of the bindings. To reproduce the spatial distribution of rigidity in a cross-section of the stator bar, the bar is modelled as a composite material comprising a conductor bar with equivalent elastic moduli and ground insulation. The accuracies of the developed binding and stator bar models are verified by comparing measured natural frequencies of binding test pieces and stator bar specimens with calculated values. The developed models and conventional models are applied to the natural frequency analyses of stator end windings, and then the effects of the modelling methods on the calculation accuracy are investigated. While the maximum calculation errors of the conventional models are more than 12%, the calculation results of the developed models agree with the measured values within an error of 7%. Accordingly, for accurately calculating the end winding natural frequencies, end winding finite element models need to take the binding rigidities into account and reproduce the rigidity distribution of the stator bar.