Finding a simplified model for a stator end winding field

A variety of generator problems are associated with end winding vibrations. Long-term end-winding vibrations with a certain excitation frequency close to the 4-node natural frequency of the end winding (in the case of 2-pole turbo-generator) can cause severe failure in the end winding region. Due to complex structure of the end winding region including strapping system used to tighten stator bars and also limitation of computational resources, finding a simplified model to estimate the vibration behaviour of the end winding unit is of great interest. In the current paper, at first, the natural frequencies of the end winding unite are acquired via the modal test. Afterwards, the simplified model for the end winding is found through finite element method aimed to equalize the natural frequencies of the proposed simplified model with those obtained by the experimental test (Modal test). The results showed that the proposed simplified model covers the critical 4-node and 6-node as well as bending natural frequencies and corresponding mode shapes of the end winding region and can be used as a suitable pattern for various end windings units with analogous arrangement.