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Forum Index : Windmills : help me find used 10kw pma motors please
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goldhunter_2 Regular Member  Joined: 10/03/2010 Location: United StatesPosts: 57 |
very interesting idea karl I had already planed a three bar or cage support if you will for the turbine but it never crossed my mind to add a 2nd generator, though it may take a little extra force to get started with two |
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Dont take my bluntness to seriously, my bark is worst than my bite, but see what happens when you think outside the square, and look at other surgestions. Now you have a more practical solution with 2 genetators off 1 mill. If you stepped a little further outside and considered AXfX you could stack the plates with magnets and coil disc's back to back as many as needed to give the current you are looking for. You could also switch in more wimdings if needed as the rpm picked up. Because there is no iron core involved in a AXFX generator there is no drag or cogging, as in a PMG or F&P so the startup wind speed is much lower. If you get the design on the coils wrong then you just remake the disc with the coils in it, and the disc's with the magnets remain the same. Its not a total loss and is able to be changed if needed without the loss of the biggest exspence being the magnets. A generator is relient on the coil windings suiting the rpm at the nominal operating speed. The only way you will achive this is ...1.. buy a ready made that has proven data to support the requirements you need. Or...2 build your own to suit your application. Or ..3 keep looking for a very rare 10kw PGM motor that will give more problems than it will solve due to startup drag inherent to the style of motor. Whoof >>>>>>>>>>>>>> (Ahhhhr thats with a "WH" and no"P" Pete. Sometimes it just works |
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niall1 Senior Member  Joined: 20/11/2008 Location: IrelandPosts: 331 |
heres an alt i came across a while back 10k 
i think they are axial flux (the smaller units certainly are) and suspect the price is astronomical but certainly seem rare and interesting 50k ? 
i was told by a dealer here that the us military use this make (windro?) for some of their stuff so if thats the case someone in the states is importing them erm...i,m not recommending them or anything like that , hopefully some owner feedback might filter through at some stage niall edit...sorry Perry you already mentioned this alt... didnt check your earlier link properly...  niall |
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| goldhunter_2 Regular Member Joined: 10/03/2010 Location: United StatesPosts: 57 |
niall1, The fact that they mite have been used by US military is a good lead I get engine to do aircraft conversion for local airboat form guys who buy surplus military stuff and we do wind testing for a company on military tents so I'll have to ask around and see if anyone has access to some of those, thanks Downwind, we all have allot more bark then bite  and I do like thinking outside of the box , I really did consider those other options before I got to this point. I am reconsidering a tower mount mostly because I may have found a ready made base pole fairly cheap
I really did like karls idea about using dual generators it provides the possibility for twice the output with minim added expense. today's winds are a little lighter at 25mph with guest into the 30's some days are much more some are less but the dual setup could make good use of heavy wind days I am not opposed to the AXFX and I guess that I know there different but still consider them a PM type alternator/generator witch may not be political correct. I would like to know more about these. When you say doesn't have a Iron core to prevent clogging are you referring to the resin cast coils for the stator ? can't it still clog just not as easy? when you say stack them are they done with one plate magnets both sides or two plate flush with magnets one side each? and one more long winded question  and these again may be two different things that I am consider similar but on the AXFX I see the coils are in the middle and flat but for example a jet ski uses a stator that the coils are warped inside and the magnets outside work with magnets in flywheel ..... what and why the difference? when ya'll build these type of generators is there any way (like a formula)to estimate the size for give min-max rpm's of the unit other then after it is on the mill? |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
The jet ski will have the coils wound around metal poles or iron core. An AXFX is just the copper wire wound into a coil set in resin. No ferrious metal used in the coil construction. So there is nothing to cause cogging or drag. The stator is fixed and a metal plate each side of it with the magnets attached rotates past the face of the coils. One thing i dont recall you saying is what voltage you are intending to generate. Pete. Sometimes it just works |
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| goldhunter_2 Regular Member Joined: 10/03/2010 Location: United StatesPosts: 57 |
at this point I am still open minded on voltage but was leaning towards the ac form the mill to rectifier (inside) to 24V dc with a battery controller for back up system (optional to be added later date)then to a grid tie inverter . allot of that depends on the type of generator unit I end up with at least in my mind. do you have reccommendations ? does one way produce a more effective power output then the other or is it mainly the clogging issue as a difference ? what is the max RPM the internals of a AXFX generator can safely spin ? reason so I would be able to calculate the gearing required. |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
i,m not sure if one is more efficient (or robust) than the other (others could comment better on this) ...but in one way the lack of cogging and drag as Pete mentioned makes an axial especially suitable to lower wind power harvesting...theres not a lot of power in low wind but its nice to take advantage of it they start up easier and seem to always run in a kind of standby mode waiting for that slight increase in wind speed , lack of drag in the alt would seem to suggest better efficiency an iron core stator may be more efficient at focusing the field through the coils but axial alts can compensate for this with the use of stronger magnets , the availability of neo magnets moved on their cause a lot the max rpm is maybe more down to the quality of thrust bearing , balance and the rigidity of the magnet rotors matching the coils (load ?) would be critical gearing an axial seems more tempting than an iron core but i havent seen it done ...gearing seems to be a bit of a moot point ....  niall |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 574 |
hi goldhunter Have you made up your mind up if are you going to set up 10kw generator??? if you do send some photo thanks
Ian |
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Sonny Regular Member Joined: 17/01/2010 Location: United StatesPosts: 66 |
Might want to take a look at these. turbine a complete novice |
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| goldhunter_2 Regular Member Joined: 10/03/2010 Location: United StatesPosts: 57 |
Sonny , thanks but I absolutely positively do not want a HAWT style mill Dwyer, I am differently starting around 10Kw system or if I go with karls suggestion maybe to 5KW for lower torque or lower gearing. My son just wrecked one of the Porsche's last night so the legal bills mite slow me down a little but will post picture when I get farther along niall1, so then your saying anything the bearings can handle is fine there would not be a overload form excess RPMs weather it is 400 or 4000 (numbers just for reference to make point) The bigger the generator the higher the amount of torque required in either bigger turbine or gears to start turning it form what I can see so gearing needs to be considered or huge blade design. we call gear boxes "torque multipliers" but the correct ratio is very important to swing the right prop or this case turbine. if a low ratio would work I could use some gear noses form lycomings I already have laying around but if the generator produce more power with more RPM a higher ratio would work much better or at least that is my thinking right now |
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| Sonny Regular Member Joined: 17/01/2010 Location: United StatesPosts: 66 |
Goldhunter, you might still want to contact those folks anyway. You never know, they might be able to work something up for you to use on a VAWT. I have found that just by asking sometimes you may be surprised what you might find. a complete novice |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
The whole point of DIY AXFX is you can build it to suit the rpm's required. ie no gearbox. design it for a cutin speed of 100rpm and it will make max output at say 300rpm. The trick is going to be working out how fast it will spin, could be lots of trial and error. From what i've read diameter = low rpm and height = speedy thus id think 200rpm or less would be max to keep it all from flying apart. coils are cheap to make as downwind suggests so its a balance, larger diameter = faster magnets thus more power 5kw should be achievable out of a 20" stator easily, but im thinking that works out at (educated guess-there is a post on working it out properly) 48 2"x1/2" neo's a side thus 96neos per stator. thats getting expensive! SO phills 12" stator has seen 3KW at 600rpm or so using 24 2" neos thus perhaps a 16" stator would be better and (again guessing) 24 neo's a side, 48 each end 96 in total. this is now beyond me but Gordon and OZ nut this kind of stuff out for kicks, again i'll follow with interest. I just hope (for your sake) you didn't burn the Gordon bridge! -intentionally or otherwise. 24V and 10KW BTW is tough - 10,000W/28V = 357Amps that alone i'd think would be enough to reconsider the voltage you want/need. consider this Power one do a 6KW wind inverter (grid tied) which you could design around for 5KW. when you find the thing maxxed out all the time (which i doubt) add the second 5-6KW stator and 2nd inverter. these thinks like a few hunderd volts which effectively cuts down the amps considerably EG 10,000/ 400 = 25A. this is far far easier for the electronics to handle. not to mention the losses trying to push 300+Amps through anything short of railway iron size copper and the massive expense that would be. so here we are..... everything else i've read on the forum suggests the opposite way around, build a mill THEN build a generator to suit what it does. unfortunately building it is going to take some serious time. a Lenz type turbine seems to be the one people here have had some success with. any other type is going to need lots of smaller blades and its all going to get really hard to manage quickly. Luck favours the well prepared |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
i think on the electrical side high rpms aren't a problem but again it comes back to the rotors..most diy axials have the magnets just glued on or set in a potting compound , this limits their use in high rpm situations as you dont want things flying off , if there was a way around this the rpms wouldnt be as limited failures in magnet adhesion on exposed rotors in axials can be one of their weak points , if any become loose or corrosion seeps in the results arnt pretty niall |
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| goldhunter_2 Regular Member Joined: 10/03/2010 Location: United StatesPosts: 57 |
Naill1, does anyone commercially offer magnets or has any DIYer's even drilled magnets to use a hard mount and make them more secure? (I know other DIY machinist have drilled magnets with masonry bills lite chipping an diamond bits and must be keep cool because there toxic and flammable ) KarlJ, I have noticed most of the commercial 10-12kw units are around 20-21" in diameter unless it is a stacked or geared unit Building to suit the DIY needs is great I am all for that ...lol, but did I misunderstand doesn't any pma or axfx type generator produce more power at higher rpm then it does at a lower one? I don't really mind the gear box actual like the idea to be able to decrease the turbine size and increase the torque/rpm's to generator internals plus I would think if it runs a little higher rpm on low wind days it would increase efficiency one other point I guess I should mention and I may be thinking of it incorrectly is when I say 10KW generator I don't expect it to be consist at that just that that is the max expected to be able to handle . sometimes the way I word things in type don't express exactly how I am thinking about them unfortunately |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
torque to drive the generator i dont believe is such an issue, nor is efficiency at low rpms just as efficient if not more efficient than high speed, all comes down to the size of the wire used for current handling and low resistance and the speed/density of the magnetic flux. If you wind the coils for 100rpm cutin you could use cap voltage doubler to halve the cutin speed and yet not miss out on the top end power. read the cap voltage doubler thread (38pages!) 20" means for lots of magnets and hence costly, if you can get away with less diameter you're up for less magnets or perhaps go the bigger size with 2x 1" rectangular magnets instead (seem cheaper). AXFX / PMA are built for a purpose, can wind for high rpm, less turns or low rpm more turns... again I'm out of my depth here, hoping for OZ or Gordon to chime in. Hell i couldnt even afford the magnets let alone a turbine as big as you are after. cant help but to think building a smaller one for starters and scale up from a working design. Luck favours the well prepared |
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Perry Senior Member Joined: 19/11/2009 Location: Posts: 190 |
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| DTMC Newbie  Joined: 12/02/2010 Location: Posts: 11 |
You cannot beat the physics. There is only so much power that can be extracted from the wind. For a hawt: P = 0.5 * 1.25 * pi * r * r * v * v 0.35 r = radius (m) v = velocity (m/s) P = power (kW) 0.35 = fair assumption for attainable effeciency of a hawt. 1.25 = density of air The only use for a gearbox is to correct a turbine / generator mismatch. This may be done by design. The only way to increase power in low wind situations is to increase the swept area of the blades with a suitably matched generator. However, this may come at a price in the top end. eg structural and thermal requirements/limits plus the ability (or inability) to brake the turbine. |
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| Perry Senior Member Joined: 19/11/2009 Location: Posts: 190 |
I think your missing a 'v' in that formula |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
mmm...i wondering now , adding to the coil winding count would increase the voltage at low rpm but the Hz would still be low , going to a higher rpm gives the same voltage increase effect but with a higher Hz ...is higher frequency of any benefit ? ps..there are neos available with a pre-drilled hole in the centre Ed ,fieldlines on otherpower has some reference to these i think tightening a bolt on a neo seems a bit daunting to me but thats probably shear fear on my behalf....maybe the holes are for locating pins ..check fieldlines niall |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
there are plenty of modern adhesives well up to the task. EG I had a Subaru WRX with 500HP, the DOG rings in the gearbox were Glued, yes Glued to the straight cut gears. Purpose is to lock the gear to the shaft thus takes the full 800n/m of torque i was throwing at them. dog ring wouldnt have been more than 3" diameter and `1/2" wide. I did break one eventually but that was three or four gearbox failures later (normally failed from the front pinion shaft having its head chewed off). Thus using a 24hr metalbond type adhesive there will be no issue whatsoever with magnets departing the scene Luck favours the well prepared |
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