GE Vertical Motor - Spherical Roller bearing with springs

[RM12]

I have been trying to test run an induction vertical motor with spherical roller bearing on the NDE. This bearing is inside a cartridge under which there are springs. The entire assembly goes inside the bearing housing. The DE has a deep groove ball bearing (guide bearing). The axial play was set to 0.008- 0.010 ".
During the test run (unloaded) the vibration amplitude seems to be cycling between 0.13 ips to 0.44" ips in a span of 15 mins and all at 1xRPM (1800). The phase angle of unbalance does not change by much (270 -284 deg)

What could be the cause for this? What is the testing procedure OEM follows to test run this motor unloaded?

 

[Gr8blu]

@RM12 Is your vibration in the radial or axial direction?
More details on vibration in the following links.

1× RPM Vibration is Not Always Caused by an Unbalance, Here Are 9 Other Faults - Ludeca

An eccentric part can be balanced but that does not make it round, only balanced, so internal clearances can be constantly changing.

ludeca.com

Misalignment

We can find shaft, bearing and pulley misalignment  that can be diagnosed by vibration analysis.

power-mi.com