 just wondering, difference between alternator and genera |
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| machina |
 Aug 6 2005, 11:13 AM
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#1
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Advanced Member  Group: Benefactors Posts: 2,030 Joined: 21-June 03 From: Miami Beach, FL Member No.: 848   |
what is the difference between and alternator like on a modern car and a generator like they used on older cars?
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| lapuwali |
Aug 6 2005, 11:42 AM
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#2
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Not another one! Group: Benefactors Posts: 4,526 Joined: 1-March 04 From: San Mateo, CA Member No.: 1,743 |
Both generate AC current by moving coils of wire near electromagnets, the devil is in the details. A generator spins the current generating coils and has the electromagnets be stationary, where the alternator does the reverse. The upshot of this is that in the alternator, the relatively low current required by the magnets goes through a set of brushes, where in the generator, the high generated current goes through the brushes (which generates more heat, so the brushes wear faster). The generator also does the DC conversion mechanically, by having the ring the brushes rest against be split into bits (the commutator), which only transmits the "positive" end of the AC sine wave, so you get a series of interrupted current pulses only flowing in one direction. The commutator also accelerates brush wear. The alternator, since the current generating coils are fixed, can't use a mechanical commutator, so it uses a set of high-current diodes to cut the negative side of the sine waves instead.
The alternator can generate more current than the generator for a given size mostly because it can be multi-phase. Rather than just one set of current generating coils, an alternator will have several (usually 3), all slightly out of phase with one another due to the rotational angle differences of the magnets and the coils as they spin. These multiple phases all "add up" to more current. |
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| bondo |
Aug 6 2005, 12:26 PM
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#3
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Practicing my perpendicular parking Group: Members Posts: 4,277 Joined: 19-April 03 From: Los Osos, CA Member No.: 587 Region Association: Central California |
Aren't alternators also full wave rectified as well? (flipping the negative side of the sine wave into positive instead of just cutting it off)
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| BMITCHELL |
Aug 6 2005, 07:05 PM
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#4
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Member Group: Members Posts: 328 Joined: 28-February 05 From: Moorpark, CA Member No.: 3,681 |
To my knowledge, alternators will charge effectively at idle while generators need rpm to reach full voltage. At least that's the old school theory that they told me during my hot rod days long ago. |
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| SLITS |
Aug 6 2005, 07:11 PM
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#5
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)
and The generator is long and round. The alternator is short and round (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) |
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