Numerical Simulation and Full Scale Landing Test of a 12.5MW Vertical Motorcompressor Levitated by Active Magnetic Bearings

The development of a hermetically sealed, high speed, high performance motor-compressor for subsea application was started by GE Oil & Gas in 2006. The bearings consist of Active Magnetic Bearings (AMBs) as primary bearings and angular contact ball bearing pairs as auxiliary bearings, both provided by S2M. To mitigate the risk of rotor or stator component damage in case of a rotor emergency landing from full speed/full load conditions, a new numerical tool for predicting rotor and stator dynamics during the drop phase was developed in 2007 by GE Oil & Gas jointly with the Southwest Research Institute. In addition, a scaled vertical rotor drop test rig was built to validate the numerical tool, to perform endurance tests on the auxiliary bearings and to identify failure modes and relevant predictors. The numerical tool was extended to predict the transient rotor drop dynamics of the full-scale prototype machine during field operation. As a conclusion of the extensive factory acceptance test performed on the prototype machine, a rotor drop test with five drops on auxiliary bearings from full speed/full load was performed. This paper presents the results of the experimental activity in terms of rotordynamic and auxiliary bearing performance. In addition, a comparison between measured and predicted parameters (i.e., rotor whirl frequency and amplitude) is discussed, highlighting the strong interaction between the axial and radial dynamics of the rotor on auxiliary bearings during coast-down. Finally, a detailed description of the post-test inspection of the auxiliary bearings and compressor internals is given.Copyright © 2011 by ASME