I found this thing on ebay, recently, and had to wonder: "DC to DC Step Up Voltage". It supplies constant output volts (boosts to, say, 12, no matter what the inputs, and gives the rest as boosted (or reduced) amps.
I mailed the guy and he said he has them rated for small wind turbine capacities, as well.
Does anybody use these things?
Date: Wed, 12 Nov 2008 17:38:57 +0000
Subject: Re: [s-w-h] Hub, Gear, Shaft, Bearing, Belt -- Gear Ratio -- project update
Hello Sam - I remember your name as though you were a veteran. Yes
essentially everyone uses a 3-phase Permanent-magnet AC alternator and
bridge rectifier. I have found it makes more power than brushed DC
motors, especially since the Supermagnets make up for the low RPM,
allowing a small genny to make big power! If you do the calcs on the
centrifugal force on your chain or belt around the small pully, you'll
find it pushes the limits of chain or belt. Or check the
manufacturer's specs. I am not saying it won't work, just that I went
thru this process and had to look around and say "OK this toothed-belt
thing, and the chain idea, is well-known technology and nobody in the
industry is using it, so maybe it doesn't work so well."
I could send you a photo of a very rusty chain for example - hard to
keep it oiled up there, and bird do-do doesn't help, when mixed with
Then again - maybe nobody has given the toothed-belt thing a proper
chance and maybe it will work fine. And it is not as though no
turbines use brushed DC motors, but not many, so it is not like it
won't work - it does work, but what I found is it doesn't work well
enough that you want to make more of them - then again, you might find
the magic combination of parts that works great and withstands 100 MPH
winds. That will be the next test once you're making good power: What
happens in that 100 mph gust? :)
You can match the number of poles to the original number of poles of
the motor which is 2 poles for 3600 RPM, 4 poles for 1800 RPM, 6 Poles
for 1200 RPM, 8 poles for 900 RPM, etc. (actual rated RPM is slightly
higher due to "slip".) Essentially you want to match the number of
poles of the stator. Leave 1 space between the magnets larger than
the rest of your spaces, so all magnets hit their corresponding poles
at slightly different times to reduce cogging by a large margin. It
is far easier than building an axial (cluster?)-flux machine. I am
told however that "once you go axial flux, you'll never go back", and
it may be that for a home-built single-rotor design, axial-flux is the
best way to go, but personally I am trying to make things light
weight, affrodable, simple, and repeatable. I've found that you can
get a lot of clues from industry - there is a LOT of accumulated
experience out there in the field of rotating electrical machinery.
--- In firstname.lastname@example.org
, Sam Jennings <samjennings@...>
> Hi Doug,
> It's good to hear from you! I don't know if you remember but we
talked on the phone several years ago. I noticed your website has
some nice new ideas, recently, including the balloon tethered
turbines. I had to admire it. =)
> I don't care about the forum moderation. And I'll pay attention to
what you have to say. On the other hand I have to pay attention to
what resources I already have at my disposal.
> I've proceeded with my plan in a relative information vacuum, and
now all the parts are en route; I already made the investment. I
might as well connect all the parts and see how much performance I can
get, and hopefully without problems of noise or compromises in
starting speed or burnt out dc motors (with or without teeny wires).
If there are problems or setbacks I will proceed regardless and
eventually there will be genuine progress.
> Doug, your turbines run at a higher rpm b/c of smaller props, right?
So when you describe the noise problem with belts / chains, are you
talking about a hypothetical conventional turbine or an ultra high rpm
> In terms of motor alteration, how do you choose the motor? Any 3
phase motor? AC / DC?
> What I've got right now in terms of motors: 2 100 watt dc motors
(with brushes) (and now also 2 complimentary belt driven power trains
that I'd hate to waste). & some fan motors (unlabelled, AC, not sure
if 3 phase).
> I've also got 30 neo magnets, 42 strength, 1x.5x.25 inch with poles
on flats, and 3.8 lbs of 22 awg magnet wire, all just waiting to be
turned into a (brushless) axial flux generator (i've got bearings,
shaft & hub for the same), but I don't know the right number of coils,
or how many turns per coil, or how many magnetic poles I should use to
assure a desirable watt/volt/amperage and a reasonable rpm without
risk of burning up my coils. Is that a reasonable use for those
resources, or am I better off looking for motors to convert to pm
brushless (using those magnets)?
> And I hope this isn't a stupid question, but does anybody use AC
motors to generate, and then use bridge rectifiers (for instance) to
get DC for storage to battery?
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