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| Alternators ought to last a few thousand hours each. That's about what they do in pickup or automotive service, should do a lot longer for semis and tractors.
What fails? bearings and brushes?
What speed is the alternator belted for? What speed is the irrigation engine run at? I presume it rarely idles but runs at full load speed or is parked. I'd look at slowing the alternator. Last I experimented it took some 1400 shaft RPM for a self excited (no regulator) Delco alternator to put out 14 volts. I have a 10SI on my JD4020 and I put the smallest available alternator pulley. I've not hooked up ignition power to excite it so I have to goose it to get it started charging but then it charges full rate as needed even at a 450 RPM engine idle. Its probably running four times the engine speed. If your irrigation engine is running mostly at say 2000 RPM, the pulley ratio could be rearranged to run the alternator at about crankshaft speed and get three or four times the brush and bearing life. And still would get very fine charging because of the relatively fast engine speed. The only reason an alternator is belted to run a lot faster than the engine is that makes it charge at engine idle in traffic (when the extra power is needed to run the A/C compressor clutch), and it can survive maybe 8K or 10K RPM because of the robust rotor construction. When the engine speed is rarelly slow there's no need to spin the alternator nearly so fast.
In a VW pickup I once had (made of Rabbit parts) there was a long overhang on the alternator pulley and there bearings only lasted 50K miles or maybe 1500 hours which matches your 2 month alternator life.
Then I'd check the alternator bearings for looseness every time it was shut down and I'd plan on replacing bearings when I deteted that looseness. My local automotivee electric shop charges a lot less for bearings and brushes than for a smoked alternator where a failed front bearing has let the rotor rub on the stator.
Gerald J. | |
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