[Healeys] electrc fan vs. belt drive

[Bob Spidell]

<sending in 2 parts> 


False (again, the Law of Conservation of Energy: there are no freebies). 

This is expressed in the concept of 'load.' The load on the alternator increases or decreases depending on the electrical demands placed on it. At cruise, the load on the alternator--this applies to generators, too--is more or less stable. Turn on the lights, and the load, or power demand on the alternator increases by the power needed by the lights. The alternator needs to produce more power, measured in watts, to power the engine plus the lights (the voltage regulator, which controls power to the rotor of an alternator--or to the field coils of a generator--will supply the extra 'feed' current). This additional power, measured (usually) in HP, comes from the engine. There are conversion factors that convert HP to watts, to BTUs and any other measure of energy and back. If you track it carefully, you will find that your mileage is less at night with the lights on than during the day (not much, but measurable, esp. in a low-powered auto). 



<continued> 



----- Original Message ----- 
From: "Bob Johnson" <bjsbj8 at gmail.com> 
To: "Oudesluys" <coudesluijs at chello.nl> 
Cc: "Bob Spidell" <bspidell at comcast.net>, "healeys" <healeys at autox.team.net> 
Sent: Thursday, February 5, 2009 8:24:29 AM GMT -08:00 US/Canada Pacific 
Subject: Re: [Healeys] electrc fan vs. belt drive 


There is an implication here, I believe, that the greater the power requirement, the harder it is to spin the generator/ alternator. Isn't the relationship between the engine and the gen/alt a fixed relationship between the pulleys? And following that, the the regulator controls the amount of electrical output as required to run whatever you are trying to run on your vehicle? I don't know, but it just seems logical to me that the motor turns, the gen/alt turns and the horsepower to do this work would be essentially constant regardless of electrical power requirements. If you take the mechanical water pump out of the system you would save hp requirement for the engine, IOW the engine would spin more easily. Then the electrical water pump, while requiring hp to run the pump motor would be "free" because more electricity would be released by the regulating system. It was always being produced, just not being used. Is this true or false? 

Bob Johnson 
BJ8