Engine main bearings fail due to alternator?
Engine main bearings fail due to alternator?
(OP)
I have an alternator being driven by an engine, output is 1500 kva, 600 volts and rpm is 1200. The alternator has had a supposed history of running the main bearings of the engine that drives it. We were put into a position of having to use the alternator so had the unit completely overhauled. When the alternator was installed all alignment checks were done and checked, all clearances and tolerances were within specs. The alternator was powered up and excitation current and voltages were similar to the other 3 units in the same package. The system is an above earth IT system, there was no ground fault indication. The alternator ran for 3 weeks and the engine main beaings failed. As this alternator is the only common unit for 3 engine failures it is getting the blame but I am having trouble pinpointing the cause, any suggestions.






RE: Engine main bearings fail due to alternator?
I have seen this problem b4, check the rotors winding with megger, It only takes a small leakage current (a few amps)to interuput the oil bondary on the bearings and abnormal ware will result assuming brushless exciter a small dc leakage (milliamps) will do this
RE: Engine main bearings fail due to alternator?
RE: Engine main bearings fail due to alternator?
There's no shortage of magnetic flux in the area, either. I just can't help imagining that long ago, there was an odd looking piece of metal with no apparent function inside the exciter housing, placed there to prevent magnetic leakage flux from getting into the engine structure, and it was lost or omitted during an early maintenance incident. If you look at an Illustrated Parts Breakdown, are all the parts still there?
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Engine main bearings fail due to alternator?
Also check the rotor diodes for correct insulation from the heat sink. This could be your leakage source.