Stator Core End Region Heating in Large Generators: A Case Study

High Voltage Rotating Machines (HVRMs), specifically generator stator cores, are susceptible to various operational issues that require thorough investigation and analysis. This paper focuses on several problems that may occur during operation, including overfluxing, overheating of end regions, and spark damage due to improper operation of the flux shield. While these issues originate from fundamentally different causes, their visual symptoms may appear similar, making accurate diagnosis essential. This paper provides a comparative analysis of these failure mechanisms, highlighting their distinguishing characteristics with actual examples. A specific case study involving a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$22 \text{kV}, 200 \text{MW}$</tex> generator stator core with spark damage is presented. The analysis includes failure investigation, and root cause identification. Different corrective action strategies are discussed and supported by analytical Finite Element Analysis (FEA).