Author Topic: 3.2 meter ferrite magnet MPPT wind turbine  (Read 61243 times)

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Offline ChrisOlson

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3.2 meter ferrite magnet MPPT wind turbine
« on: January 12, 2012, 01:09:11 pm »
I'm going to try to put together an orderly and informational post on my latest wind turbine build for this new forum.  Judging by the amount of private correspondence I've gotten on this project, there is HUGE interest in the concept of both using ferrite magnets in a wind turbine generator, plus using MPPT on it to optimize output of the machine.

The post, when I get it prepared, will have a lot of photos for people to look at.  The old saying is, "a picture is worth a thousand words".  One thing I could point out is that when people do post photos to the new forum, I'm pretty sure (admin correct me if I'm wrong), that it's more efficient for the host server to NOT upload the pictures to the host.  There's outfits on the internet like Picasa Web Albums (which is what I use), or the outfit that TomW uses for online photos (can't remember the name of it right now - PhotoBucket maybe?).

You can link to the photos and make them appear in your post instead of uploading them.  This reduces the CPU time on the server required to do SQL queries to pull the photos out of a database contained on the server.  It instead turns the photo into merely an external HTML request in the page code to make it display in the post.  So the server only has to do one SQL query to pull your post out of the database.  The rest of the work in getting the photo to display is done in page code when your browser renders the web page.  From what I remember about running servers back in the day, this will make the new board (especially if it gets lots of photos) run faster in the long run without getting bogged down when search engine crawlers start indexing and caching pages and images on the site.

So I'm going to try this here to make sure I understand how it works (it's the button on the left right below the "B").  You simply go to where your photo is in another tab in your browser, right click on it and save the image web location, then paste the URL in between the image tags.  This is a photo of the completed turbine on which I will try to explain the complete build in a subsequent post (might take me awhile to put it all together).



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Offline Wolvenar

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #1 on: January 12, 2012, 01:43:28 pm »
As far as CPU and SQL time go, the hardware that this sits on could handle a lot more than we need to worry about with a site like this.
However that said, the best ( in my opinion ) option is to upload images to the gallery here at anotherpower
http://www.anotherpower.com/gallery/
This gallery keeps an original sized  and resizes an image so the largest dimension is 640. This intermediate size works good to link to. Since these images are not stored in SQL it does not then cause issue there.
For todays computers running a standard resolution ot 1024/786 or more this seems to display well in a post

This also has the benefit that images are not lost in posts if an off-site hoster goes away, changes its guild lines or you have to make room for something else by deleting images when you find you have hit your storage limits.

This gallery here has essentially no size limitations, nor is there any limit on how much you can add. However it seems to have a little bit of a fit if you upload an enormous amount of large images in one upload.

Some images not relevant to RE are of course acceptable, but use common sense about stuff like that.


Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline ChrisOlson

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #2 on: January 12, 2012, 03:28:22 pm »
This gallery here has essentially no size limitations, nor is there any limit on how much you can add. However it seems to have a little bit of a fit if you upload an enormous amount of large images in one upload.

Thanks wolv - working on putting an album together of the 3.2 meter  turbine photos.

Quote
Some images not relevant to RE are of course acceptable, but use common sense about stuff like that.

Ok, photos of bikini-clad wife go in Global Warming album    ;D
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Offline ChrisOlson

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part 1 - design
« Reply #3 on: January 12, 2012, 04:30:25 pm »
All the photos here (and more that I won't post) can be viewed in the album for this turbine here:
http://www.anotherpower.com/gallery/ferrite-magnet-MPPT-turbine

The first photos start out with the gearbox design and layout.  I had decided early that this turbine was going to use an angled hinge tail, with the tail working against gravity, for the furling system.  So I offset the PTO shaft in the gearbox to move the generator slightly away from the yaw axis, and thereby allow more room for the tail hinge.  In the end, this worked out quite well.

The gearbox has a .400:1 gear ratio, meaning the turbine's generator runs at 2.5x input shaft speed.

My original idea with a MPPT-controlled wind turbine was to use a Midnite Solar Classic 150 controller on a 3.8 meter turbine, with a dual stator ferrite generator, modified with high voltage stators.  I tested this setup (with a stock stator set) with a hydraulic motor driving the turbine's gearbox input shaft, with the Classic 150 hooked up, and a "real world" wire run to my battery bank, to get an idea of how the controller works and how a stock 24V generator pans out with MPPT on it.

What I learned was that it is quite easy to get 2.5 kW out of this setup with way less shaft power input required than what a 3.8 meter rotor can deliver.  I discovered I don't really need the raw amp capacity of the dual stator generator, but I could use more voltage input to the controller to make the gen, rectifier and wire run more efficient.

I think it was about that time that I decided to downsize the turbine to 3.2 meters and use a different style of blades on than GOE222's (which is what I had used on previous turbines).

So I went to my CAD (Cardboard Assisted Drawing) design system to look at possibilities for a generator for it:


I initially looked at 10 pole stacked two-phase layouts.  But then the light bulb came on over my head one cold night and I decided to figure out a three-phase single stator layout that would give me adequate amps and more volts for the amount of rotating mass and copper used in the generator.  This is a CAD layout of coils that were actually wound for a 10 coil single phase stator.  But the pin dimensions and volt turns ended up working out fine for a 16 pole 12 coil three phase design, as well - with the added advantage of getting more volts out of the thing:


Based on my testing run, I developed a spreadsheet to figure out how to match rotor rpm and available shaft power to rpm/volt from the generator, and to the load.  My initial idea here was to have 119 open volts @ 400 rpm.  But later on in the build, after studying the NREL testing data on the S809 airfoil that I'm using, I decided I needed to run the rotor faster (480 rpm @ 12.5 m/s) to get enough shaft input power to make a 2.5 kW turbine out of this thing.  I made a YouTube video explaining that decision that you can watch (hope this YouTube thing works - couldn't get it to come up in the Preview)


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Offline Wolvenar

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #4 on: January 12, 2012, 05:29:18 pm »
Looks like some nice work there Chris
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline ChrisOlson

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part 2- transmission and main frame
« Reply #5 on: January 12, 2012, 09:08:04 pm »
On my previous geared turbines I placed the gearbox inline with the yaw shaft.  With the heavy 3.8 meter rotor and lightweight neo generator they were balanced pretty nice on the yaw.  However, once I retrofitted them with dual stator ferrite generators, the extra weight of the generator caused them to be slightly tail heavy.  Those machines had a long input shaft housing that placed the rotor well forward of the yaw.

On this one, the rotor is lighter than the 3.8 meter.  And the generator is heavier than a neo.  So I attempted to move the weight forward as much as possible.  I also wanted less offset (130 mm) with the smaller rotor.  So I placed the gearbox ahead of the yaw and inclined the input shaft at 6° from horizontal



This one will not have an input shaft housing.  This is the input assembly for it, and with the input shaft test installed in the gearbox





It looks like the rotor is a long ways out front.  But this style rotor is for a downwinder.  So the blades have a pretty radical sweep backwards at the root of the airfoil.  There's not as much room there as it looks like there is.  The blade roots clear the front of the gearcase by about 30 mm.



The tail hinge is welded on at 18° angle and 40° to the side of being straight back from a parallel line drawn thru the input shaft and yaw centerline.  I also put a spring loaded damper on the tail return



After building and welding a stator mount to it, and building the tail boom, it's ready for assembly



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Offline Dave B.

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #6 on: January 12, 2012, 11:38:03 pm »
Hello Chris,

  I got through the registration and the move successfully I guess. Great to see your latest videos on the turbine and I had to laugh at you being over ruled on the blade color. I like the look of those blades and will be anxious to hear of their performance with the new turbine. I know plenty are watching as well, let it fly !  Dave B

Offline ChrisOlson

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #7 on: January 13, 2012, 09:35:53 am »
I'm the most fortunate guy on earth because my wife takes an interest in all my wind power projects.  And she comes out and helps with the turbines especially during installation, pulling the drop cable thru the tower, helping me lift and install an assembled rotor - she even wired a stator up on one once.  So if she wants white blades on it, what the heck - white blades it will have.

Wait until she sees it run tomorrow when I finish getting the clipper built and installed.  This one is a right hand turner - the rest are left hand.  I can almost see it now - she'll be standing there with her hands on her hips looking up at it and go, "You put the blades on backwards."

And by gully she'll right once again - these blades are for a Talon downwinder   ;D
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Offline rossw

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #8 on: January 13, 2012, 02:18:22 pm »
I can almost see it now - she'll be standing there with her hands on her hips looking up at it and go, "You put the blades on backwards."

And by gully she'll right once again - these blades are for a Talon downwinder   ;D

Silly question, don't laugh!

Is there any rationale at all for the conventional anticlockwise rotation?
I mean, ok, if one had nuts and threads that would work loose - fine. But many of the commercial ones I've seen have a keyed shaft, and with a locknut or castellated nut, they're not going to come loose anyway.

Or is it just convention? The first ones were made that way, and everyone makes them that way "because thats the way everyone else makes them"?

Offline ChrisOlson

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #9 on: January 13, 2012, 03:04:51 pm »
Is there any rationale at all for the conventional anticlockwise rotation?

Yeah, it depends on which side of the equator you live on.

No - that was just a joke    8)

That's kind of an interesting question.  All major horizontal axis turbines today rotate the same way (clockwise) because it's supposed to present a coherent and pleasing view.  Early turbines rotated counter-clockwise like the old windmills, but the change to clockwise rotation happened after about 1978.  One of the blade suppliers back then in Denmark made the decision to change direction in order to be distinguished from the Tvind (in Denmark) and their small wind turbines.  Some of the blade customers were companies that later evolved into Vestas, Siemens, Enercon and Nordex.  Since public demand required that all turbines rotate the same way, the success of the Big Four made clockwise the new standard.

The only other rationale is that it's "ideal" to have the blades turning the opposite direction of furling when looking at the machine from upwind.  In other words, if you have a left hand furler, ideally you should have right hand (clockwise) rotating blades.  And vice versa.

The reasoning behind that is to help prevent a tower strike during rapid furling.  For instance, with a left hand furler, left hand turner, the bottom of the blade circle will flex towards the  tower during a rapid yaw event to the furling side.  Put right hand turners on that same machine and the bottom of the blade circle will tend to flex away from tower during rapid yaw to the furling side.

But still, which way the blades turn and which way it furls cannot "fix" an improperly designed machine that does not have enough forward "lead" of the rotor to the yaw axis.  Nor "fix" a tip-to-tower clearance problem caused by not having enough inclination of the input shaft from horizontal.  If you have adequate blade tip clearance to the tower, you won't have a problem with either one.

So basically the "standard" came to be because the human mind tends to prefer a right hand (clockwise) rotating machine, as it's supposed to be associated with symmetry somehow, or "the way things should be".  But for somebody as screwed up as I am, even that doesn't make any difference   :D
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Offline frackers

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #10 on: January 13, 2012, 04:27:33 pm »
Is there any rationale at all for the conventional anticlockwise rotation?

For me it depends on which way it furls. I changed the direction of mine as I'm sure that the generator was lifted off the yaw bearing by the gyroscopic precession forces as the mill violently furled during a large gust. According to my calculations now, during the same conditions the force will be down rather than up.

And guess what - 6 weeks ago I ended up with a bent tower which may well have been the extra downward load due to exactly those forces >:(
Robin Down Under (or are you Up Over!)

Offline ChrisOlson

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part 3 - the generator
« Reply #11 on: January 14, 2012, 06:41:09 pm »
After making the decision to use a single stator three-phase generator on this turbine, this was obviously going to require bigger diameter generator rotors than the dual stator two phase ferrite units I had built in the past.

My CAD (Cardboard Assisted Drawing) indicated that I could get the magnets to fit on 355 mm diameter rotors with just a tiny bit of room to spare (~2-3 mm) between the corners of the big 51 x 51 x 25 mm thick C5 ferrite blocks.  I machined the rotors true and to 5 mm thickness, plus milled some lightening holes in them to reduce rotating weight:



This is a finished rotor - they ended up at 10.4 kg (23 lbs) each.  I also welded "claws" on these rotors, like I have done with my other ferrite generators, to hold those heavy magnets against centrifugal forces.  There's a lot of confusion over putting the "claws" on the outside of the mags, as this is supposed to "steal" flux.  But I did a lot of experiments when I built my first ferrite generator, and determined it doesn't make one bit of difference.

One thing about this layout is that I'm "wasting" the corners of the magnets by placing them this close together.  I'm getting the same flux in the air gap as I would if I used wedge-shaped magnets.  But being these magnets are readily available, and cheap ($1.84 each), the extra cost of having custom wedge magnets machined is not worth it.



Then I turned a pile of coils into a stator - it's wired wye, 45 turns of 13 AWG per coil, it ended up at .55 ohm internal resistance.







The initial test after assembly of the generator showed it produced 119.1 open volts @ 1,000 rpm with the air gap at 18.5 mm.  I later tuned this back just a tad by opening up the air gap to 19.5 mm so it would produce 115.4 open volts @ 1,200 rpm.  This will let the rotor spin 480 rpm @ 12.5 m/s instead of 400 rpm, and still maintain the max 100 volts (loaded) that I want to operate the generator at at full power.  I don't want to tune for over 100 volts to allow some "breathing room" for the Classic controller if the turbine were to become unloaded due to over-amp of the controller.

The voltage clipper will come on (controlled by the Classic's Aux 2 output) at 145 volts.  But the clipper is a three-phase wye resistor @ 6 ohms, and can only handle 3 kW of power for a short time.  If the turbine were to unload due to over-amp, hopefully the clipper will keep its operating voltage under the controller's 150 volt limit.  This remains to be seen, as it hasn't been tested.  You can rest assured I will monitor it very closely with my hand on the emergency shutdown the first time we get 15-20 m/s wind, until I'm convinced it works properly.

Now all that's left is to put it together and get it on the tower.
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Offline halfcrazy

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #12 on: January 15, 2012, 06:08:33 am »
Chris
Very nice work. I love following your posts and wish I had the time to try something new.

Ryan

Offline bj

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #13 on: January 15, 2012, 07:18:02 am »
   Chris--quick question--what kind of tape did you use on the coils?  You may have said, but couldn't find
it.
   Thanks in advance.
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bj

Offline ChrisOlson

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Re: 3.2 meter ferrite magnet MPPT wind turbine
« Reply #14 on: January 15, 2012, 09:53:58 am »
bj, I bound the coils in this one with regular old 3M painter's tape.
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