Soft foot & 120Hz was a new one for me, we'll check it out. Probably you have nailed it, since our techs just noted we never check for soft foot, & this machine was just aligned.
Thanks much!
Good research on vanstoja's part. I'm thinking information overload, at this point. Looking at this from a practical predictive maintenance standpoint, the 0.2% voltage unbalance is better than many places I've seen. Rotor out of round may cause 1 per revolution fundamental acceleration that is...
Further to the current unbalance comment, one thing I haven't gotten a good grip on is how negative sequence rotor currents can cause a mechanical event observable by vibration instrumentation. If the rotor has suffered damage, I would think you would see much more activity around bar passing or...
Further to the previous, (checking my facts) that is a 6 pole motor, 500hp, and is operated in (unusual for this app) continuous mode, with Multilin reporting 232 starts in 7824 hours, voltage on bus balanced within ~0.2%, one leg current 2% higher, ~matching one voltage leg reporting low. Other...
I found this post looking for an answer to a vibration technician's finding of a 120Hz vibration in a 4 pole induction motor, >200HP. This machine had been subject to excessive vibration earlier due to coupling mis-alignment, also has a rather severe duty cycle for an industrial application...
