The only job of the regulator is to turn on and off the field windings inside the alternator based on battery voltage and turn off the charge indicator light on the dash.
If you think there is no draw from the alternator turn on all the electrical accesories in your car and note the rpm drop.

The alternator is a magnet and a bunch of wires going around in a circle. If the wires were generating current (electro magnet) then it would cause the magnetic fields of the natural and electro magnet to interact with each other and perhaps add to the load on the engine.

[edit]
Ah see here I am thinking of a generator. So the alternator is an electromagnet and a stator. I see as the load increases the regulator increases the current in the electromagnet there by increasing the physical resistance of the rotor interacting with the stator. Now I see. How is this more advantageous than a generator? Heat issues with the disappation of the extra energy?

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Why do you need a 10 hp motor to turn a 5200 watt generator? You could probably spin the armature by human power without a load, but plug in a heater and you're not going to spin it.

Winmutt, the force required to spin the alternator is DIRECTLY proportional to the instantaneous electrical load on the system.

__________________
1987 Mercedes 300D

Which is why regererative braking works on EVs and hybrids.

Sixto
... stay tuned

a generator/altanator uses electromagnets to convert mechanical energy into electrical energy.
the more electrical load on the altanator, the stronger the current passing through the windings, hence the stronger the magnet will be pulling against the iron stator. the stronger the magnetic field, the more hp is required to turn the winding.
directly proportional to power used. perhaps you are correct in that the altanator is designed for a specific power output, and that output will not change by rpm, but the regulator will drop in and out the field based on demand.
Hmm, perhaps you are confusing power with amperage... the same 14.4 volts will be produced no matter how much you turn the rpm's due to the VOLTAGE regulator bringing in and out the circuit.
imho
John

Early alternator-equipped Harley-Davidson motorcycles did have this property, as they used a permanent-magnet field and a shunt-type regulator. However, even with these, you could install an aftermarket regulator which did not shunt the excess current, and thus would free up just a bit of power.

But even typical automative generators would control the field current to affect the output voltage, which does cause the input power to be somewhat proportional to the output power (there is always some loss). All automative alternators that I've ever seen do this.

A good example that an alternator puts more load on the engine when providing more power is seen on modern cars too, when I jumpstarted a car with our minivan, when cranking the car I was jumping, the van raised its RPM's on its own by probably 300-400rpm to compensate/produce extra power. The car's computer saw the huge power draw, and rev'd the engine in response, it then dropped back to normal idle when the load was gone. Pretty cool. The van itself is junk, but I thought the high tech compensation was cool.

I can tell on my SD when I power on the CC, rear window defroster, headlights, etc...the rpms do drop by 50 or so, you can tell by the sound.


Here's an idea, put a huge amp capacity alternator on your car, then fully load it, and try a 0-60 run, compare it with the times with no load on the alternator. A 120+ amp one can sap over 10hp off the engine under heavy load....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Also note when a huge load is on the alternator how hot it physically gets,and how it drags the engine rpm down trying to carry the load.

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Winmutt,

One more thing, you can't dissipate current or voltage. Only power (watts) can be dissipated.

P E H

Also for those that are not aware of what a zener diode is. Some people know what one is and some do not as it is not that common an item in the everyday experience. At a pre designed voltage point it conducts. Probably about 12-14 volts on the english bikes. If it conducts to ground for example it has to disperse the heat from the power dissapated internally. Much the same a a resistor getting hot. Hence the heatsink. Below it's trigger voltage it remains basically an open switch. The zener diode is a very useful electrical component available in a wide range of conducting voltages. Think of it as a tap. At a certain water pressure (voltage in our case) it automatically starts to flow to eliminate the excess water pressure. As soon as the water pressure drops below it's initial turn on point it automatically turns off. Many applications but not practical basically for dealing with large power as a self standing device because it can be done cheaper and better and less wastefully by other methods. Also on the thrust of this post you have to waste power/energy to heat the zener diode up as the generator is dealing with a constant load when it serves no useful purpose other than preventing overvoltage basically. Poor engineering to some extent in my opinion.

You, sir, are wrong.

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In any of my posts, it is safe to assume
that I'm talking about this car.

Zener Diode

Wiki

One of the places the Saturn Greenlines get their mileage boost is basically an alternator that can turn off. I believe they call it the smart charging system. I don't feel like typing all the details but my uncle part of the development team and I have access to a lot of the tech info.

__________________
Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

Yes and no. In a generator, natural magnets are used hence the same power is always generated, the regulator dissapates the energy. On an alternator that magnetic field is regulated by the regulator. So in reality an alternator is much more efficient than the generators of old.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42