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Old 05-14-2021, 01:51 AM   #26 (permalink)
Isaac Zachary
High Altitude Hybrid
Join Date: Dec 2020
Location: Gunnison, CO
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Avalon - '13 Toyota Avalon HV
90 day: 41.06 mpg (US)

Prius - '06 Toyota Prius
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I wonder how you could make an alternator more efficient...

I'm trying to remember how they usually work. If I remember correctly the voltage regulator shunts current through the rotor which cause an alternating current in the stator (or is it vise versa?) In any case, if you could use thicker wire without reducing the number of windings, that would help.

Now if the rotor's current is controlled by means of resistance you could instead control current by means of pulse width modulation instead to help increase efficiency. A permanent magnet rotor could be even more efficient, but then you'd have to think of another way of controlling voltage and current.

The rectifier is another point of energy loss. Using more efficient diodes may help. But more efficient diodes may not tolerate as much current. So lowering max current may be necessary.

Lowering voltage can also help by not charging the battery up to the point that it's self-discharge also raises. Although in theory your alternator could be more efficient if it ran at higher voltages/less current (more turns) and feed a higher voltage battery. Of course then there'd be DC to DC losses from the higher voltage down to 12V unless you completely rewired everything to use the higher voltage, including modding the ECU and any other place where voltage is stepped down for use in electronic chips and also your have to build your own ignition coils. But all this would probably not be worth the trouble.

Also, I don't remember if the rotor is wye wound or delta wound. A wye wound rotor would be more efficient, but the voltage and current would be different without changes in wire thickness, length and number of turns.

Another area of loss is the housing and rotor construction. You want them (or at least the housing) to be made out of very thing lamanates that are electrically isolated from each other made of an iron alloy with a very low hysteresis.

Of course if you have a lot of stop and go traffic, maybe making the alternator come on only while decelerating would help.

Last edited by Isaac Zachary; 05-14-2021 at 02:57 AM..
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