Re: using a motor as a generator


leeps wrote:
Im not worried about efficiency for power in vs power out its more for
dealing with heat, same thing but what i meant was would the alternator
run cooler than your "average" permanent magnet generator. I didnt
realize that treadmill motors were dc what voltage, i might pick some
up just to play with. A problem though is this thing is supposed to be
towed behind a bicycle so i think that might be too heavy. if its in
the 10-15 pound range and not too big it might be perfect. Ive been
looking around surplus places and my main problem is there are no specs
sometimes they just show a picture and say "12vdc motor 3000 rpm 1.4
amps" should say "good luck" right after it too. I wasnt really
worried about burning up the engine, I was saying that i dont think the
540 mabuchi motors would make a good generator because of heat
handling, mine has .2 ohms of armature resistance so at 25 amps im
looking at 125 watts of heat. I cant imagine a small motor like that
dissipating this kind of heat. I plan on having the unit controlled
with a pic microcontroller, with temperature sensors amperage shunt
voltmeters etc , basically going as far as the resources in the pic
will let me with 33 i/o lines and 8 k program i should be able to get
good control. Anybody know of proven pmdc motors that take about 30-40
amps continuous ( that dont cost a million dollars nor weigh a million
pounds). continuous power ratings also seem really really hard to come
by for the average non industrial motor. I know it seems like im
being difficult here but i cant find a good motor, i could just use the
small car alternator but maybe there is a good motor out there that i
dont know about.

I mooched around and found this with a brief Google search:
http://www.treadmilldoctorstore.com/s.nl/sc.2/category.26/.f
pm motors that are only a few inches in diameter and have 2.5 to 3
horses for $150.
Doesn't say how much they weigh. Would be cheaper if you wait until
they show up at some surplus house.
I've never tinkered with this stuff, but I think you get ac from a
brushless dc motor converted to generate electricity. Maybe you could
use the diode pack from a car alternator to rectify it.

.

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