Field tests for veryfying stator core laminations loose in 3-phase, 3000 HP motor
An indication of loose stator lamination would be vibration at precisely 2X line frequency and possibly harmonics of 2X line frequency. If the vibration ceases immediately when power is shut down, is absent with the motor coasting, that indicates loose stator laminations or some other electrical fault. It is probably not possible to verify in the field. If you search the internet you should be able to find additional information.