D
Dominic-Luc Webb
Guest
On Mon, 29 Dec 2008, Eeyore wrote:
conventional, at least classical, automomotive and marine
alternators are 3 phase brushless generators with no
commutators and the schematics I have been able to find for
these show a slotted stator with coils and a rotor with
permanent magnets. This looks essentially same as the
homemade wind generators I have seen so far. I know that
some "alternators" are actually DC generators with solid
state diodes. I do not know how to tell one from the other
when I am in the junkyard, but that is maybe a separate
question.
Is is not so that a true automotive/marine alternator uses
permanenent magnets? I know the marine ones are built to
not produce sparking that could ignite fires in engine rooms.
I now think 3 phase is my starting point, so let us assume
I will stay on this track. For wind generation, I note
that nearly all the small scale and home made wind generators
are using 12-18 slot stators (and 3 phase). As compared to
the 2 slot alternator, this implies the goal is to be able
to get 50/60 Hz at comparatively low RPM. The automotive
ones achieve their relative high RPM by using a pulley ratio
with the comparatively slower engine at idle, engine
have the larger pulley.
Is there any reason why I should not just use a car
alternator (if they have permanent magnets) and similarly
also use a pulley to get more RPM if needed?
Also, does anyone know how many poles or slots on a car
alternator and roughly how many RPM when the engine is at
idle (ballpark)?
Dominic
I am not following this actually. From what I can find, theTim Wescott wrote:
My first guess at a quick & dirty generator would be a car alternator,
at least if you just want 12VDC from lead-acid batteries. It's very
best feature is that if you pick one that's common then replacement
parts can be found at the nearest junkyard (or the nearest neighbor with
the right vehicle, if you're not terribly scrupulous).
They're pretty inefficient. Permament magnet alternators can do much better.
Graham
conventional, at least classical, automomotive and marine
alternators are 3 phase brushless generators with no
commutators and the schematics I have been able to find for
these show a slotted stator with coils and a rotor with
permanent magnets. This looks essentially same as the
homemade wind generators I have seen so far. I know that
some "alternators" are actually DC generators with solid
state diodes. I do not know how to tell one from the other
when I am in the junkyard, but that is maybe a separate
question.
Is is not so that a true automotive/marine alternator uses
permanenent magnets? I know the marine ones are built to
not produce sparking that could ignite fires in engine rooms.
I now think 3 phase is my starting point, so let us assume
I will stay on this track. For wind generation, I note
that nearly all the small scale and home made wind generators
are using 12-18 slot stators (and 3 phase). As compared to
the 2 slot alternator, this implies the goal is to be able
to get 50/60 Hz at comparatively low RPM. The automotive
ones achieve their relative high RPM by using a pulley ratio
with the comparatively slower engine at idle, engine
have the larger pulley.
Is there any reason why I should not just use a car
alternator (if they have permanent magnets) and similarly
also use a pulley to get more RPM if needed?
Also, does anyone know how many poles or slots on a car
alternator and roughly how many RPM when the engine is at
idle (ballpark)?
Dominic