Alternator temperature limits ?

[veggie]

I am planning to encase a Changfa 175 inside a sound enclosure so that the unit can run 8 hrs per day without the neighbors hearing it. (Inside the garage).
The Changfa will be driving a 24 volt alternator.
One concern is heat buildup inside the cabinet.
The heat from the engine can easily be removed through an external radiator, but in order to keep noise levels down there can only be minimal air flow through the cabinet.
Does anyone know the upper limits of automotive alternator temperatures?
The alternator will be running at 1/2 of it's full amperage capacity which should help somewhat.

[mobile_bob]

most automotive alternators, made for the trucking industry have a design limit of at least 205F and many newer versions (last 15-20 years) are made to handle 220F iirc.

i thought of doing just what you are talking about doing, with the case and all, but also drive an A/C compressor to use as a heat pump to draw the internal heat from the enclosure and move it to the house where it would be put to use.

i think that could be done with the 175, with a control scheme to cycle the compressor and while it was pumping freon the alternator could be cut back to a lower output to not overload the engine.  keeping it near max output would make for maximum efficiency, whether at 80% or whatever you design for.

the heat exchanger i designed and built for exhaust heat recovery on the s195 trigen, was designed to be a batch fire system. in that the unit was only designed to operate for an hour or so, twice a day. it used the condensation to self clean after each startup.  running only an hour or so the unit did not build up enough carbon so that the condensation available could not keep it clean. not sure how it would fair with longer run times, i never tested for that. and i never tested for other than max output of the engine where the amount of soot is minimal to deal with.

i think maybe the little stainless steel egr coolers might be worth working with. it would be interesting to find out how much heat could be recovered using one, and how well the clean themselves over time.

a good indicator of how well they recover heat, is the difference between the temp going in, and the temp coming out of the exhaust.

i got lucky with my design, the heat going in at max output on a 70F day was 640F and the heat coming out was 240F which is above the boiling point of water, keeping the exhaust hot enough to not condense and cause issue with the remaining exhaust system.

the system could raise 60 gallons of water from 70F to 140F in an hour of operation, that on 70F ambient temp days which was typical in tacoma during the month or so i was doing all the testing.

i ran over 50 test runs and all the temps remained stable, which told me the unit was not only functioning well, but also able to self clean.  had the unit over time not been able to raise the 60 gallons of water by 70F and the temps coming out of the exchanger started to rise, i would have expected things were starting to carbon up internally.

bob g
bob g

[mobile_bob]

i got it a bit wrong on the temp thing

the 555jho alternators are able to stand 125 centigrade
that works out to 257F

so they can stand some pretty high temperatures
the older versions were 105C or 221F

either way, they can stand some pretty high temperatures, and i would expect all automotive alternators are built to the higher end of this range, given the underhood temperatures being quite high it is hard for the alternator to shed its heat so i would sure have it spinning upwards of 4k rpm or more so that its fan could pump as much relatively cooler air as possible.

the 110-555jho as used in the white paper i wrote 13 years ago, (has it been that long?) i got the alternator to charging 28.8 volts at 100amps in 70F ambient continuous duty and the stator never exceeded 175F and everything else i could get the heat laser to access was under 175F that included the rectifier diodes.

running at 130amps and 28.8vdc the heat only rose about 10deg
which was still well under the alternators 120c design

the temperature was measured at 5 minute intervals and after 30 minutes of testing i quit as the temperatures did not rise further.

fwiw

bob g

[veggie]

That's very useful info Bog G. Thanks.
I feel a bit more comfortable about enclosing it with the engine.

cheers,
veggie

[Tom Reed]

I can share, since I've been dealing with it a lot. Standard bearings are rated for 160F and the C3 bearings are rated for 250F. So that would concur with Bob's high estimate of 257F.