Welcome! Please use the navigational links to explore our website.
PartsASAP LogoCompany Logo Auction Link (800) 853-2651

Shop Now

   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver

Tractor Talk Discussion Forum

Alternator drag on RPM?

Welcome Guest, Log in or Register
Author 
Jim Holtby

03-05-2007 13:27:24




Report to Moderator

I was curious about why engine RPM drops when alternator is working against heavier amperage draws. Is it the EMF that causes the drag or braking effect against engine RPM? I never really knew what phenomena was involved. Is there any actual added wear to the physical componets of alternator when it's responding? Thanks for any enlightement!




[Log in to Reply]   [No Email]
KEB

03-05-2007 20:43:14




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
Conservation of energy - energy is neither created nor lost, it can only change form (except in nuclear reactions). The alternator simply converts rotational (kinetic) energy that it gets from the engine into electrical energy and heat. Bigger load on the alternator means it must get more energy from the engine, hence increasing the load on the engine.

There have been any number of triestes (sp?) written on the mechanisms that convert kinetic to electrical energy instide a generator (or alternator), but for this discussion it really doesn't matter what the mechanism is.

Keith

[Log in to Reply]  [No Email]
MarkB_MI

03-05-2007 19:42:03




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
You didn't ask why your engine lugs down when you're going up a hill. But it's exactly the same thing: the engine is doing more work; whether the work is against the alternator load or to go up a hill, it's the same thing.

I doubt that it makes much difference to alternator life whether it's run under heavy or light load. The total number of revolutions is what adds up the wear.



[Log in to Reply]  [No Email]
frankiee

03-05-2007 18:43:33




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
Electricity is with magnetism and magnetism is with electricity. Cant have one with out the other. Electricity is (dare I say) created by the like poles of a magnet being forces to oppose each other. The strength of the magnet is controlled. The more powerful the magnet, the more powerful the output but, the more power has to go into forcing the magnets by each other.
Everytime we turn the headlights on the more we have to strengthen the electomagnet and the harder the engine has to work to overcome the magnetic repultion. We burn more gas because the engine has to work harder; everytime we turn on a light or radio or whatever.

[Log in to Reply]  [No Email]
RayP(MI)

03-05-2007 16:57:30




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
I have a 60amp alternator on a tired 5hp tiller motor. When I put it on a mostly discharged battery, thet will make the motor bark pretty good. Most of today"s automotive alternators are in the 100 amp range. That"s enough to draw several HP on a full load.



[Log in to Reply]  [No Email]
dave guest

03-05-2007 16:32:45




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
Did you ever go wormin" with a crank generator? Wetter the ground harder to crank. If somebody stuck the wires together, you could hardly turn it. Same with alternator, gets harder to turn when workin' hard.



[Log in to Reply]  [No Email]
dave guest

03-05-2007 16:32:25




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
Did you ever go wormin" with a crank generator? Wetter the ground harder to crank. If somebody stuck the wires together, you could hardly turn it. Same with alternator, gets harder to turn when workin' hard.



[Log in to Reply]  [No Email]
RAB

03-05-2007 16:14:58




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
A 750 watt alternator is putting out a horse power at full load. Automotive alternator is probably no better than 75%, and probably quite a bit less with all inefficiencies taken into account, so when you consider an engine is only "making" just enough energy to keep itself runnning, that extra one, to one and a half, horsepower is noticeable, either slowing the rpms or opening up the governor to compensate.
Regards, RAB

[Log in to Reply]  [No Email]
Sam#3

03-05-2007 14:00:29




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
It's called the LOAD. When the alternator is asked to supply more EMF* as when the lights are turned on it requires more work from the engine to turn the alternater. No different than connecting to any other load. I've always been surprised at just how much power they require. *I suppose if you want to use the proper term, ElectroMotive Force, you can but a more common way of saying it is voltage

[Log in to Reply]  [No Email]
Walt Davies

03-05-2007 13:58:56




Report to Moderator
 Re: Alternator drag on RPM? in reply to Jim Holtby, 03-05-2007 13:27:24  
Its the old adage you can't get something for nothing. For every ampere that you get, you loose HP at the engine. Walt



[Log in to Reply]  [No Email]
[Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:


TRACTOR PARTS TRACTOR MANUALS
We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

Home  |  Forums


Copyright © 1997-2023 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters

Website Accessibility Policy