In the paper you listed, they showed a 4%increase in efficiency(at 14vdc output) by using a constant 4amp field excitation voltage. They did not generate the excitation voltage from the alternator, but from a seperate power source
Quote:
A DC power supply was used to energise the field windings with 4A.
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. How much power does it take to generate a constant 4amps? The standard alternator set up in their test used up to 50 watts of its own output(variable draw). If it were 50watts, just to make things equal between the two modes, wouldn't that draw a higher percentage of the alternators output at lower engine speeds and/or alternator outputs?