Research Article

Using Simplified Models to Assist Fault Detection and Diagnosis in Large Hydrogenerators

Table 7

Natural frequencies of 1st Backward Precession Mode (BPM), 2nd Forward Precession Mode (FPM), 3rd BPM, and 4th FPM, with generator excited and unexcited.

Bearing clearance conditionNatural frequencies [Hz]
Generator excitedGenerator unexcited
1st BPM2nd FPM3rd BPM4th FPM1st BPM2nd FPM3rd BPM4th FPM

A4.715.127.187.915.245.747.287.93
4.845.307.237.935.355.897.337.95
B4.194.707.087.864.845.367.167.87
C3.113.776.957.794.014.597.027.80
D3.114.196.997.804.024.917.057.81

The symbol “”indicates that the shaft position is different. In the clearance condition A the pad clearances are in the nominal values (200 µm) and the shaft is centered at coordinates (0,0). In clearance condition A* the pad clearances are once more in the nominal values but the shaft has an eccentricity of 67 µm.