Finding the right generator

[Murcott]

Hello Everybody,

I am building my own wind turbine. I need a gearless (direct drive) three phase generator. I'm making a really small turbine that produces 200W at wind speeds of 6 to 8m/s. The generator needs to operate at a low rpm to minimise the size of the gear box . Aorund the 500rpm mark would be perfect, anything more than 1000rpm is too much.

I'm having trouble finding suppliers on the internet. Ebay is sort of useful, but I'm struggling to find exactly what i need. Can anyone reccommend some decent sources/suppliers?

Cheers,

Murcott

[dnix71]

"Really small"? That makes 200w at those wind speeds? I have an AirX. It's about 3 feet in diameter and tops out 300 watts in a gale. I've seen it hit 200 watts in severe weather. Not the kind of weather you can be outside walking around in.

To get 200 watts you need minimum 6 foot diameter at 18mph (8m/s).  And a tower tall enough to get into clear air.

Is your location that windy all the time? 200 watts of solar would be much easier. 500 watts name plate of solar is $450 including shipping.

http://www.ebay.com/itm/2-Pieces-250w-Watt-Poly-Solar-Panels-Christmas-Deal-/221638623000?pt=LH_DefaultDomain_0&hash=item339ab0ff18  You ought to get 200 watts real power out of a pair of 250's. at least several hours a day.

[SparWeb]

Many ways to skin this cat:
Convert a 3-phase industrial motor the way I have:  www.sparweb.ca
Build an axial-flux alternator according to the Hugh Piggott plans.
Build an even bigger one according to the homebrew plans on this forum's host site: the Otherpower.
Convert a Fisher-Paykel smartdrive motor like the folks do down under at "the Backshed".
Purchase a servo motor of suitable size from e-bay.
Purchase a DC motor of suitable size from e-bay.

The key will be matching up the generator to the blades.  Oversizing, undersizing, there are more ways than one to render two good components useless because they don't work together.  Do you already have blades made or selected?

Fortunately, we've seen it all here, so if you tell us more about what you need to do, we can give you the right steer.

and...  Welcome! 

[Murcott]

Thanks for the tip SparWeb, good to be here on Field Lines.

Dnix71, I'm embralled with this Wind Turbine melarkey at the moment. Solar panels are for another day.

I am building a VAWT to demonstrate an idea. The blades have a frontal area of about 1 m. sq. hence why I expect to get about 200W. The blade size is determined by the limited amount of space I have, the build only serves for demonstration and testing puposes.

I've made my own generator before. It was a three phase dual rotor axial flux alternator. I quickly learned that building such things is best left to an expert equipped with the right tools, which I am not. It worked but the efficiency was pitiful.

The VAWT will operate between 60 and 200 rpm, which is quite low. I could use a DC motor, but surely I'd need a gearbox as DC motors operate in the 1000s of rpm. I suppose I could try a 1kw motor (for example) which should give 200W ish, at low rpm. However, this could be expensive, clumsy and inefficient?

The best i've found so far is the following:

http://www.ebay.co.uk/itm/like/12V-i-500-generator-wind-or-hydroelectric-energy-500W-wind-turbine/131378080539?hlpht=true&ops=true&viphx=1&_trksid=p2050601.c100274.m3472&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140723104424%26meid%3D851c8ab109c94be4a6efe067cba7939e%26pid%3D100274%26prg%3D20140723104424%26rk%3D2%26rkt%3D4%26sd%3D131224745334%26clkid%3D2842875353921689430&_qi=RTM1793705

Any thoughts?

[electrondady1]

they say there are incredible winds on Venus.
 difficult to  get 200w out of 1sq.meter here on earth.

http://www.usvawt.com/cgi/windpower.cgi

[dnix71]

Ditto what ElectronDaddy said. You won't make 200 watts with one square meter. All the power is produced at the edges. That's why bigger blades are better.

You will make 25 watts in real life with a sail that size.

[Murcott]

Ok, don't worry about the blade size, i can change that. Back to my original question, where can I buy a 200W generator?

I think i'll take a look at what SparWeb has suggested. Although I am surprised no one can suggest a specific supplier.........

[electrondady1]

a lot of people here really enjoy making their own alternators.
 store bought is just ok.
modifying an existing devise to a new purpose is also considered sexy.

a couple of 10" saw blades would provide enough backing for a alternator that could harvest what a 1sq.m. vertical could produce.

[dnix71]

200 watts is too small to be commercially useful. Even a small car alternator puts out at least 40 amps at 14.5v

If you could find an old VW Beetle generator that might work, but I think those were 6v nominal.

If you bought a 500 watt permanent magnet gen from a sleazy eBay dealer, it would probably be a 200 watt gen in real life and be a good match.

A lot of those overrated gens are only capable of the rating if you can find some way to keep them cool. Run them way under the nameplate and they are safe.

A old treadmill motor would probably work. I got a ceramic magnet motor from a junked treadmill and hooked it up to a 2HP Briggs engine on a sidewalk edger frame. It would put over 100 watts into a car battery using a capacitor and full wave bridge to smooth some of the wild ac from it. It couldn't put out much more than that without stalling the engine. It was belt driven about 1:1.

[DamonHD]

I've got a *nominal* http://www.futurenergy.co.uk/ 1kW generator sitting in my shed in London that you could have if desperate.  I will never get to deploy it, though I do occasionally use it in a demo to schoolkids!  It cogs fairly noticeably.

(48V-nominal 3-phase delta-wired.)

Rgds

Damon

[Murcott]

Good point Dnix, it wouldn't make sense to mass produce a 200W generator. Guess I'm going to have to get my hands dirty again. Thanks everyone for the ideas for units to convert. My last attempt really was from scratch . Wound the coils, adhered the magnets, built the circuitry etc. Hopefully converting a commercial unit will be more productive.

Damon, my last company worked closely with FuturEnergy and I spoke with the founder on a couple of occasions. Seemed decent enough. Their 1kW generator is just what I need, just a little over rated. Out of interest, how much would you want for it?

Cheers,
Murcott

[Mary B]

GE ECM motor would be a perfect match at this power level. Can be direct driven too. But not from 1m blades!

[DamonHD]

@Murcott potentially the grand price of zero if you promise me that it'll get a good home and save some carbon, and you can make getting it to you painless!

PM me if you want to follow up.

Rgds

Damon

[soundbite55]

Hi

As a newcomer to the wind generation club I want to adapt a washing machine universal motor and create a PM generator for a VAWT as my initial project.  I naturally have a number of questions before I can take the next step so any assistance is greatly appreciated.

I disassembled a Bosch ~ 450w universal motor, separating the stator & coated armature so that I can workout the best arrangement for the magnets. 

1. Having decided to file horizontal channels / rows across the width of the arched em stator plates to countersink the magnets, the question arose “how large / powerful should the magnets be?”

Since I'm aiming for the lowest rpm to begin generating current from ≥24v dc but also need easy start-up for lighter winds, is there a straight forward answer to the magnetic field needed or some formula to work this out? Each of the 2 stator plates is 60mm wide and 65mm high (dia) and I thought 5x magnet 10mm (H) x 44mm (W) x 4mm (D) rows each side would fit nicely but is that too much / little?  A set of bar neodyms I saw listed a pulling power of about 4Kg (8.8lbs) each (think they were N45s).
 
2. Also, would it be better to remove the stator coils; will they add to or interfere in any way with the over all generated field?

3. Because I am having to mount the magnets on the stator I'm not sure of the polarity orientation.  Most diagrams I've seen place the magnets on the rotor relying on the stator coils to generate the opposing fields.  One pm stator illustration I found had the orientation similar that on my diagram.

I know there are motors better suited for this but this is all I have to work with, needing to keep costs to a minimum while learning about the technology.

[electrondady1]

i think you have picked the worst possible motor to convert to an alternator.
go to an automotive scrap yard and buy a d.c. motor. (as in a rad cooling fan or a heater fan).
if you spin a dc motor it will create current.

[soundbite55]

Thanks for that, electrondady1.  As mentioned, I am stuck with this one and have to make the best of it (if possible).  Scrapyards are few and far between in my area of Scotland.  Scrap parts are expensive here and you have to remove them yourself - something I'm not fit to do. Even the recycle centres here will not allow you to take anything away.  I am tied to a small budget and really want to learn about this technology where it is sometimes better if you have to overcome obstacles like this.

Cheers.

[electrondady1]

there have been a lot of motor conversions posted over the years there should be something in the archives.
motor conversions is not my area of expertise but generally speaking a motor with more field coils is used . as in run coils and starting coils.
 yours will only be two poles

do you have a lathe ?
the armature needs to  ground down to provide space for the magnets.
what sort of budget do you have for magnets .

[soundbite55]

No, I don't have a lathe.  I budgeted £20 ($30 US) for the magnets,  I will have a look at the fieldlines archives and see if there is anything similar.
Thanks.

[Flux]

Probably the easiest way of getting something out of this motor is to remove the field coils, cut the curved pole Pieces from the rectangular yoke and cut out enough metal there to fit neo blocks behind the pole pieces.

It will then become a dc generator but realistically don't expect much from it. It is inherently high voltage and high speed so at low speed on a VAWT don't expect many watts.

The alternative is to cut away the curved poles and cut back the projection where the coils sat as before and use rectangular blocks of neo, which will be entirely the wrong shape, I think you will need much less neo if you keep the pole shoes, it will most likely cog badly if you get much magnet in there but you may be able to skew the pole shoes to help in that respect.

Flux