If they run the motor bearings under use will fail even if oiled or greased. After bearing have set for years the grease or oil settles off the bearing or dries up and the exposed area starts to corrode and pits.
Very cool. Had no idea they were still around. These old 600s make a heck of a noise on startup. Little pull and twist low voltage start/stop switches from a remote panel. BAHHHwwwwOOOSH! Any time they have to be worked on the breakers get removed from the MCCs
We have dozens of 4160v motors up to around 1000hp, with the larger ones being 4160 - 13KVA up to ~10000hp.