In a message dated 97-08-12 05:13:28 EDT, kinderlehrer@mindspring.com
(Kinderlehrer's) writes:
> Ok, now I'm very confused. The output of the alternator is dependent on the
> rotation speed of the armature, ie RPM of the engine.
Not so! The output is controlled by the regulator. As long as you have a
minimum RPM, the output of the alternator will go up and down, depending on
the load.
> Unlike an air
> conditioner, there is no clutch mechanism that engages and disenges, so if
> I put an electric fan in the car, then I have to go faster to get more
> horsepower to the fan motor??
No! As long as the system voltage remains at 12 volts, the fan motor will
draw just what it needs, and no more.
> Does this mean I will get better gas mileage if I turn the radio off? :)
Yes, absolutely! Although the difference will be so small as to be
unmeasureable, without sophisticated instrumentation.
> I guess I'm lucky because I have a TR3 with a generator which is far less
> than 100% efficient. It keeps on turning even after the battery is charged
> up and it isn't really needed, so I can use those wasted revs to drive my
> electric fan (when I get one).
Reapeat after me - "YOU DO NOT GET SOMETHING FOR NOTHING!!!!" The ONLY source
of energy in a car is that provided by the gasoline! If you turn on a light,
the wattage required to operate that light comes from the alternator, which
gets its energy from the engine. The energy in the battery, after the initial
charge from the factory, comes from the alternator, which - GETS ITS ENERGY
FROM THE ENGINE!
When the alternator (or generator) is spinning, but no electrical loads are
on, the regulator cranks the output down, and the alternator is only
consuming enough energy from the engine to overcome frictional losses. If you
could arrange to have all the electrical loads come on at once, ie, a master
switch, and you listened carefully, you would hear the engine load up, and
the rpm drop, as it takes on the additional HP drain to drive the alternator.
One horse power is the equivalent of 745.7 watts. The total electrical load
on a typical LBC is about half that, so it takes about 1/2 horse power to
drive the alternator at full load. One half horse power is so small that it
is easy to overlook, but it is there never-the-less.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition
'68 MGBGT---organ donor for the '74
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