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Fusion
Newbie
Joined: 29/11/2009
Location: AustraliaPosts: 5 |
| Posted: 05:30am 01 Dec 2009 |
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Hi I'm new to the forum and I'm interested in building a AX flux generator. Where can I get hold of Gordons cals on wire size, windings and etc. that Phill was talking about.Just to give me a starting point.
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oztules
Guru
Joined: 26/07/2007
Location: AustraliaPosts: 1686 |
| Posted: 08:23am 01 Dec 2009 |
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Fusion, the starting point is the start. Sounds trite I know, but it is true.
You first must decide on how much power you want to address, and from that you will get an idea of the prop size that will get you there in your wind regime.
Once you have nailed that down, it becomes a matter of building an alternator suited to that prop size.
You need to match the alternator to the prop, or it will perform from very average to very badly.
If your after lots of power, then you will need lots of alternator, as more power means bigger props which lead to slower RPM, which means bigger alternator.
Once you have decided on prop size, we will know what Rpm you will be developing your power at, and can then move on to disk size, magnet size..... wire size coil geometry, and lastly turns... which will be related to wire size because we have to fit it in the stator.
Until then it is a how long is a piece of string type of question.
Do you have any starting place in mind?
.............oztules
Village idiot...or... just another hack out of his depth |
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Fusion
Newbie
Joined: 29/11/2009
Location: AustraliaPosts: 5 |
| Posted: 08:40am 01 Dec 2009 |
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Trevs 2.5m aerofoil blades looking good and I'm aiming at 1-2Kw that will be enough. |
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KarlJ
Guru
Joined: 19/05/2008
Location: AustraliaPosts: 1178 |
| Posted: 11:01am 01 Dec 2009 |
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go for Trevs 2.9m blades.
The blades are going to be the cheapest and easiest part about it.
Luck favours the well prepared |
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GWatPE
Senior Member
Joined: 01/09/2006
Location: AustraliaPosts: 2127 |
| Posted: 12:56pm 01 Dec 2009 |
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Hi Fusion,
I had hoped that anyone making one of these alternators would be able to do it from the concepts.
The unit I made, and that Phill made were based around phsical limitations of a 12" ID steel pipe.
My original stator has far too many turns, should have been operated on a 120V system, but it still produces up to 1kW, with help from caps on a 48V system. Phill has managed up to 3kW on a 48V system. The 24 x 2" x 1/2" magnets and 9 coil arrangement that fits inside a 12" pipe should be good for 2-3kW when operated at 300-500 rpm. The series/parallel combination of turns of the 1.25mm enamelled wire is fixed by system voltage. I had a magnet separation distance, where the coils have to go of 18mm.
If the power is more conservative at 2kW at 400rpm, then this simplifies the windings. My coils were wired in 3phase star, with 3 coils in series per phase. For a 48V system, I would wind coils with 70 turns of 1.25mm wire on a 50mm x 16mm thick former. This will give a coil width of approx 15mm. How well the coils are wound, will affect the physical size and whether they will fit in the space for the stator. For 24V system, the number of turns would be halved, but will require 2 wires in hand. This will result in an alternator with 1/4 the resistance.
I am in the process of building a mk2 unit. This will have slightly stronger magnets, and slightly more plate separation.
If the design is changed much, ie bigger dia plates, more powerful magnets etc, then I would suggest making a test unit, as I did. Single turn testing will give accurate prediction of V/turn at a particular rpm and simple scaling will give the number of turns required for the system voltage.
I made an open style test unit, that allows the coil to be inserted from the outside, with the magnets able to be moved on the plates, and the plate separation can be varied at fixed spacing increments. I tested different coil shapes and sizes and settled on the round hole with an inner hole dia the same as the magnet dia.
I think oztules made a similar test unit.
I do not think that it is possible to accurately predict the number of turns etc without making a test unit with the magnets that will be used, in as close as possible the goemetry of the final alternator.
Phill and I premade coils that were impregnated with resin and cured prior to final wiring and casting. Others make loose coils and use a guiding system to align the coils during casting.
If you get things close to optimum, then a 2-3kW machine is on track, but as Oztules has pointed out, a badly performing one can easily result. The stator in Phills AxFx mill is thinner than mine, with a closer magnet gap. This results in a higher volts/turn, so his unit needed only 64 turns per coil, while mine had 100.
The idea is to cram as much wire into the stator while achieving the lowest phase resistance with just enough turns to provide a cutin between 100-200rpm. If you wish to use a voltage boost[caps or electronic] arrangement, then load matching becomes easier. The wire size comes back to phsical aspects. Thinner wire is easier to wind, but can result in more difficult terminations. I opted for 1.25mm for 48V system, with expected max current of about 40A.
Perhaps you might answer some questions at this time.
Do you have any idea of the wind reigime where the windmill will be placed? Have you any windspeed data?
You say that you think 1-2kW will be needed. How many kWh do you think the windmill will need to provide per day?
My own windmills have approx 1.5kW total max output. Some days the windmills make over 5kWhr. Other days output can be 0kWhr.
Will the windmill be connected to an RE battery loading, or are you looking at a GTI system?
Will you be making the bearing housing? Will you be having the rotor plates laser cut? Do you have access to a machine shop and welding equipment?
The magnets are quite dangerous to handle near iron and other magnets. I have heard of accidents with crushed fingers from individual magnets and crushed hands from accidents during assembly.
The alternator is only a small part of a complete windmill. This alternator has a stub axle type design. The attachment of blades and then the attachment to the yaw box needs to be decided upon.
I could go on and on but for the moment there are enough unanswered questions.
BTW, the wire size I used was 1.25mm. This is the size that I used, as it was the size that my supplier had that was not a full 20kg spool.
Gordon.
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Fusion
Newbie
Joined: 29/11/2009
Location: AustraliaPosts: 5 |
| Posted: 09:46pm 01 Dec 2009 |
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Hi first I like to thank everybody for the information.
My main idea is to have the windmill feed into the battery bank ( at the moment I have 6 second hand 2V Sonnenschein battery's pretty good condition )than have the electrician to disconnect the light circuit from the meter box connect a lead to it and have two power point's next to it one on the house circuit and one feed by the inverter. So when the wind don't blow and the battery's are empty I have the back up of the grit. But for the moment I will be busy answering Gordons quuestions.
thanks for all the informations javascript:AddSmileyIcon(' ')
Ill be back..... |
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KarlJ
Guru
Joined: 19/05/2008
Location: AustraliaPosts: 1178 |
| Posted: 09:25am 02 Dec 2009 |
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Gordon
lots of us have AX-FX dreams and I note Phill has said he would cram in a few more turns next time, is it possible to have an open design, ie like the f&P where it can be re-configured for different voltages as required by the end user.
I appreciate this may be a compromise BUT...
is it possible?
Obvoiusly grid connect is the best solution for this kind of thing as as you say some days are 5KW and other 0KW, this necessitates either huge battery bank or wasting much of the generated power
Karl
Luck favours the well prepared |
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GWatPE
Senior Member
Joined: 01/09/2006
Location: AustraliaPosts: 2127 |
| Posted: 12:38pm 02 Dec 2009 |
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Hi Karl,
the main point with an AxFx alternator is the ability to design it right without having to rewire. My stator was horribly wrong, as I made it to test the casting process. As it turns out caps have made it work, so I did not need to make the best electrically matched stator straight away. I have enough wire for a few more stators yet. Phill got to run with the real deal. My next stator will be on the money. I am building a sister mill, that will be almost the same. On the matter of reconfiguring windings. I see no point really. If you get it really wrong at least you know whether too many, or too few turns was the problem. If you make one stator, it is likely a second or third would be possible to make as well.
I am not a fan of purpose grid connect with a windmill. So much is about location and wind regime at the site. I use batteries to smooth out the wind energy peaks, and stop the windmill during periods of excess power. Wind usually follows the 80-20 rule. 80% of the time there is 20% of the energy. The GTI has to handle the peaks, so you need a GTI that is essentially 5x too big, and this ties up a lot of capital.
I have used a battery/inverter combo for the windmills, and solar GTI. The best depends on the personal priority. I think a hybrid system is pretty good.
OFF grid systems have to be designed with considerable surplus generating capacity. It is a balance between generating capacity and storage. These days the solar is becoming cheaper to install than batteries. Windmills need to be located at a good site.
The legislation will hopefully be ammended to allow all RE to be grid tied.
Even the purpose GTI windmills shutdown with overspeed, or stall limit, or furl. Design the alternator/windmill for the average wind at the location and you will be on a winner. Automatic furling or braking takes care of the storm type events.
Gordon.
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oztules
Guru
Joined: 26/07/2007
Location: AustraliaPosts: 1686 |
| Posted: 10:09pm 02 Dec 2009 |
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Karl, it is more than possible.
In the earlier days before they were fully appreciated, folks at Otherpower built them with all the coil legs coming out of the stator.(9 coils, 18 leads hanging over the side to play with)
They could go from star to delta as the power in the wind increased, or if they had wished to, they could reconfigure all the coils independently. You could parallel up all the normally seriesed coils and have a very low voltage high current animal too if you wished.
However, as Gordon points out, this is not a usual occurrence, and you should design the stator for your purpose.
This does not mean that there is no variance allowed. As Gordon has wound a HV stator, and successfully uses it as a 48v stator. Mine is nominally 48v, but I use it for charging the electric car at 36v. In this case I also built a second set of blades with more torque and wider chord to drive the same stator much more efficiently at low wind speeds.
Everything is interdependent, so usually a stuff up here or there can perhaps be mitigated somewhere else in the system.
It,s simple, build the device and wind a test coil. Calculations will maybe get you in the same post code, but not nearly as close as a simple test coil.
Some folks have wound 2 or three in hand for the coils and bought these out independently as well. You can then then series or parallel these in hand coils to triple or double the coils output... and remember the next coil may be paralleled.... the outcomes are numerous....(insulation between the in-hand coil potentials may be problematic long term.) but no combo as good as a dedicated stator for a single purpose.....
The reason..... stacking......... stacking in the most weight of copper for the least resistance into the stator gap will allow for the most power and the least heat... nemesis of the resin stator when poorly designed and/or well designed but overdriven..... at least you can turn it off though.
............oztulesEdited by oztules 2009-12-04
Village idiot...or... just another hack out of his depth |
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KarlJ
Guru
Joined: 19/05/2008
Location: AustraliaPosts: 1178 |
| Posted: 07:26am 03 Dec 2009 |
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when I say grid connect I mean via a battery and an LAtronics PVE 1200.. as you suggest a 96V PVE 2500 would be a fair chunk of capital to outlay $4K+ for an inverter and a 96V battery bank is insanely expensive.
I'm considering a 24V re-wire now F&P for just that reason, 24V "appliances" are available (pumps etc) and
with an expected output in the order of a few hundred watts is easily handled by the PL20 prior to the outlay of another $2K for a grid tied solution.
seems tough to justify a 2K inverter for a peak power of 300W!
Karl
Luck favours the well prepared |
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