Abnormal Vibration Problems in Large Turbine-Driven Generators and Their Solutions

Some unusual causes of abnormal vibration in large turbine-driven generators, are presented along with extensive test data on a 416 MVA generator equipped with many internal thermocouples and vibration transducers. The behavior of this and other large generators after a period of operation appeared to indicate buckling of the stator laminations is occurring which lowers the natural frequency of the core structure in the elliptical vibration mode. Moreover, experience has also shown that internal temperatures within the core structure sometimes affect the natural core frequency.