[bestclimb]

Originally Posted by wobombat

so how exactly does it work that the higher electrical load places a greater electrical load on the engine? Considering that the rotor in the alternator will spin at the same speed as the engine regardless of electrical load, how does the electrical load put a load on the rotor? Does it somehow put drag on it with the magnetic field or something? I'm confused as to how this would work.

Yes the alternator is harder to turn when putting out more power.

amps X volts = watts (a measurement of work/power)

RPM X torque / 5252 = horse power (a measurement of work/power)

So work done with electricity is replaced with work done by spinning the alternator.

If the RPM does not increase the torque has to goes up.

If the output of the alternator was the same all the time (would have to be it's peak rating) the extra energy given off would have to be dumped likely into a heat sink for a car running an 80 amp alternator at 14 volts makes a little over 1000 watts. A quick search for 1000 watt heat sink shows them to be 14 lbs of aluminum inches and finned to cool it for when you were not using all of the alternators capacity. The volume of such a heat sink is about 380 cubic inches, I have never seen such a heat sink on a car.