I have face a new vibration problem in 1600 kW AC motor which is associated with fan. in this equipment vibration is high in vertical & Axial direction in motor Drive End & Non Drive end vibration is more than 3.5 mm/sec in axial direction whereas horizontal vibration is 0.85 mm/sec.
Motor has 8 pole , and that time running rpm is 337.5.
Wondering is that we found a peak in vibration signature at 30337.5 cpm and amplitude value is 3.20 mm/sec . also find side band of 6.25Hz (337.5 cpm) around this peak.
fan side vibration is less than 0.7 mm/sec.
and Time Wave form is modulation pattern.
I dont know what is the problem. can any one help me