Modelling the vibration behaviour of stator end windings

Some stator components of large power-station alternators are sensitive features in the mechanical design of these machines. These include in particular the parts at the ends of the windings, outside the core, called “end winding cages”. These structures are complex, mainly because of their geometry and the variety of materials used. They are also subjected to large electromagnetic forces in both steady-state and accidental operation. Their durability is essential both for safety and for uninterrupted service by the alternators. It is for these reasons that a three-year research and development project was initiated to characterise the structure in modal terms, evaluate its response to various loading, and if possible establish criteria for monitoring in operation. After describing the structure and the physical phenomena involved, the article presents the approach taken in the project, which includes the use of various experimental and numerical methods. The modelling part is then described