Go Back   AnandTech Forums > Social > Off Topic

Forums
· Hardware and Technology
· CPUs and Overclocking
· Motherboards
· Video Cards and Graphics
· Memory and Storage
· Power Supplies
· Cases & Cooling
· SFF, Notebooks, Pre-Built/Barebones PCs
· Networking
· Peripherals
· General Hardware
· Highly Technical
· Computer Help
· Home Theater PCs
· Consumer Electronics
· Digital and Video Cameras
· Mobile Devices & Gadgets
· Audio/Video & Home Theater
· Software
· Software for Windows
· All Things Apple
· *nix Software
· Operating Systems
· Programming
· PC Gaming
· Console Gaming
· Distributed Computing
· Security
· Social
· Off Topic
· Politics and News
· Discussion Club
· Love and Relationships
· The Garage
· Health and Fitness
· Home and Garden
· Merchandise and Shopping
· For Sale/Trade
· Hot Deals with Free Stuff/Contests
· Black Friday 2014
· Forum Issues
· Technical Forum Issues
· Personal Forum Issues
· Suggestion Box
· Moderator Resources
· Moderator Discussions
   

Reply
 
Thread Tools
Old 08-18-2002, 03:16 AM   #1
RU482
Lifer
 
RU482's Avatar
 
Join Date: Apr 2000
Posts: 12,610
Default How fast does an car's alternator spin?

i.e. how many RPM of the alternators shaft does it take for an alternator to being producing voltage? Figure a typical alternator from...say, a chevy lumina (off of the top of my head)
RU482 is offline   Reply With Quote
Old 08-18-2002, 03:23 AM   #2
PsychoAndy
Lifer
 
Join Date: Dec 2000
Posts: 10,735
Default

It would depend on engine RPM and the size of the core as well, wouldnt it?

-PAB
PsychoAndy is offline   Reply With Quote
Old 08-18-2002, 03:32 AM   #3
Thegonagle
Diamond Member
 
Join Date: Jun 2000
Location: Minnesota, USA
Posts: 9,774
Default

Off the top of my head, perhaps 1600-1800 RPM for 12-14 volts. It's going to make a higher voltage at a higher RPM, of course, which is in turn regulated back down to about 14 volts. I'm making this guess based on the relative size of the drive and the driven pulleys, and a typical engine idle speed. AFAIK, an automotive alternator needs voltage from a battery to energize the rotor magnets until it starts rotating fast enough to energize the rotor on its own.
Thegonagle is offline   Reply With Quote
Old 08-18-2002, 03:32 AM   #4
OrganizedChaos
Diamond Member
 
Join Date: Apr 2002
Posts: 4,526
Default

it shouldn't have to spin very fast at all to produce a voltage, if you want to charge anything with it though it will have to spin quite fast. upwards of 5000 rpm. keep in mind an alternator needs power to make power on the inside its just a big spinning electomagnet.
OrganizedChaos is offline   Reply With Quote
Old 08-18-2002, 03:35 AM   #5
RU482
Lifer
 
RU482's Avatar
 
Join Date: Apr 2000
Posts: 12,610
Default

Hmm, so in a typical car, how much current does the battery provide TO the alternator vs how much current does the alternator provide to the battery?
RU482 is offline   Reply With Quote
Old 08-18-2002, 03:35 AM   #6
notfred
Lifer
 
Join Date: Feb 2001
Posts: 38,244
Default

note engine's RPM, note diameter of crank pulley. Note diameter of alternator pulley.

Should be simple calculation with a little bit of pi and some long division after that.
notfred is offline   Reply With Quote
Old 08-18-2002, 03:41 AM   #7
Evadman
Administrator Emeritus
Elite Member
 
Evadman's Avatar
 
Join Date: Feb 2001
Posts: 30,980
Default

You are way low. Most alternators will not put out any appreciable amperage until they hit about 1000 RPM. Highest amperage ratings are usually found in the 5-6000 RPM range. ever notice how increadibly small the pully is on your alternator? Like the size of a silver dollar. Alternators are usually made to spin at 3x engine speed. 2.5 would be minimum.

Without an aftermarket stator and windings, RPM over 6000 will not generate any additional amperage.
__________________
Dan (Schmin) 1981-2003. Rest in Peace
I want to drinkify all my snacks. Chewing is for people living in the 19th century.
My Blog
Evadman is offline   Reply With Quote
Old 08-18-2002, 03:44 AM   #8
Evadman
Administrator Emeritus
Elite Member
 
Evadman's Avatar
 
Join Date: Feb 2001
Posts: 30,980
Default

Quote:
Originally posted by: redly1
Hmm, so in a typical car, how much current does the battery provide TO the alternator vs how much current does the alternator provide to the battery?
Current to an alternator is less than 5 amps. Surplus from the alternator goes from 65 amps on up. Most cars now have 100 amp alternators stock. I have a 220 amp alternator to power my onboard welder. 400+ Amps are possable with aftermarket windings and stators for RV's and such.
__________________
Dan (Schmin) 1981-2003. Rest in Peace
I want to drinkify all my snacks. Chewing is for people living in the 19th century.
My Blog
Evadman is offline   Reply With Quote
Old 08-18-2002, 03:47 AM   #9
RU482
Lifer
 
RU482's Avatar
 
Join Date: Apr 2000
Posts: 12,610
Default

interesting....just thinking of trying a little homebrew windmill experiment with some parts I've got laying around.
RU482 is offline   Reply With Quote
Old 08-18-2002, 03:57 AM   #10
Evadman
Administrator Emeritus
Elite Member
 
Evadman's Avatar
 
Join Date: Feb 2001
Posts: 30,980
Default

Quote:
Originally posted by: redly1
interesting....just thinking of trying a little homebrew windmill experiment with some parts I've got laying around.
Now I remember you. from HT. Man, I am slipping. time for me to get some sleep. Night.

__________________
Dan (Schmin) 1981-2003. Rest in Peace
I want to drinkify all my snacks. Chewing is for people living in the 19th century.
My Blog
Evadman is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 11:07 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.