Vibrations of turbine-generator units caused by waviness of the specular surface of the thrust bearing disk

Conclusions

• 1. Operating experience and tests of units established that in the frequency spectrum of vertical vibration of loadbearing spiders of generators there is always a segment frequency equal to the product of the rotor speed per second and number of bearing segments. The segment frequency of vibration is manifested more strongly on units having large distance between segments in the bearing.

• 2. When designing hydroelectric generators, it is necessary to avoid coincidence of the number of segments with the number of other elements of the thrust bearing (number of ribs of the bushing, number of bolts fastening the disk to the bushing, etc.), since such coincidence can cause increased vibration of the support structures of the generator with a segment frequency.

• 3. When designing new and reconstructing old generators, it is necessary to avoid coincidence of the natural frequencies of the spiders and other structural elements with the segment frequency in order to avoid resonance phenomena.

• 4. The most effective way of eliminating resonance vibration of individual elements of a unit or structure with a segment frequency at existing hydrostations is to change the number of bearing segments, i.e., to change the frequency of the disturbing force.