Abstract – High speed generator and motor failures due to stator endwinding vibration have become more prominent in recent years due to extensive repair costs as well as lost production that are often associated with such failures. The vibration is a response to the electromagnetic forces created by the current in the stator windings. Excessive vibration levels can be attributed to loosening of the support system or mechanical resonance where the structural natural frequencies coincide with the frequency of the electromagnetic force. Insulation abrading or failure by copper fatigue can result if left for an extended period of time. IEC 60034-32 and IEEE 1129 describe methods to monitor endwinding vibration on-line with fiber optic sensors in a way that the onset of looseness can be identified, and the support structure repaired in a timely manner. A 288 MVA, 21 kV steam turbine driven air-cooled generator with endwinding vibration data prior to and after a system event that led to the loosening of the support structure was trended on-line until suitable repairs could be made and the vibration levels returned to normal.
Index Terms — Stator Winding, Two-Pole Machines, Endwinding Vibration, Motor, Turbine Generator.