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Old 01-31-2018, 03:23 AM   #368 (permalink)
Stubby79
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Quote:
Originally Posted by ASV View Post
it seems counterintuitive but the large alternator is more efficient than the small alternator. The closer to max capacity an alternator is the more it heats up.
Hot copper is less conductive than cold
if you want your alternator to be more efficient give it some nice cold air
and don't over size the pulley
at higher RPM it easier to produce the necessary power and is better able to cool itself

the only problem I can think of at the moment with the higher RPM is air resistance in the cooling fan
I would think having the "right" size alternator is the more effective way to go. You're probably right that you don't want to stress it to it's limit, but at the same time, I would expect efficiency to go to heck is you were only using a fraction of it's potential output. If it's anything like an electric motor (and it is), it would be most efficient at it's peak sustainable output. Any more and efficiency starts to drop off. Notably less and it very quickly drops off.

There are things other than the size of the wire inside that affect efficiency. This is A/C we're talking about...eddy currents and switching in the rectifier and whatnot.

Just a random alternator efficiency curve, showing that more RPM is less efficient. (Of course, it only shows full output, and partial loading will be less efficient)



Reminds me of the efficiency of an ICE. Or perhaps a TDI.
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