SC1 CC5 Failure
We believe the following sequence of events occurred around 330am on 3-10-2017
Intermittent rotor displacement alarms began about 230am but they were not long enough to force the magnetic bearing cabinet to shutdown the compressor. Eventually the alarm latched and the compressor was shutdown. The first part of the shutdown seemed normal with cold compressor speed slowing. After a few seconds it appears the motor drew full current and the speed dropped to zero instantly generating a mag bearing power defect alarm and a variable frequency drive overload alarm. Its likely the motor drew enough current from the power transformed to cause the incoming voltage to drop long enough for the mag bearing cabinet to conclude the incoming power was going off so it attempted to switch to battery back up but the motor had already seized by that time. When the crew arrived the mag bearing cabinet could not get the position of the rotor to a satisfactory position. The radial bearing appear to be very unhappy and the control cards are attempting to power the magnets to adjust the position of the rotor unsuccessfully.
Techs switch CC4 and CC5 mag bearing cables and saw the same behaviour on CC5 motor with the CC4 bearing cabinet connected. Once CC4 bearing cabinet was reconnected to CC4 it work as normal.
At this point we are unsure if the failure was due to the mag bearing cabinet or a failure inside the cold compressor itself.
This Sunday morning we reconfirmed the status of the bearing cabinet and cold compressor.
Note in the early 1990's that the original CEBAF project purchased 4 CC's and 4 MB's
In the lated 1990's JLAB purchased 6 CC's and 6 MB's. FIve were used in SC2 and one set was used in the rebuilding of SC1..
