Author Topic: Stator, Rotor size (Read 1403 times)

trumpets3u · « **on:** February 09, 2009, 10:46:56 PM »

Just asking here. If you used the 20' turbine stator and rotor size and put a 10' propeller on it would you get more watts? As I said I wouldn't do this I just would like to know.

Thanks Brian

trumpets3u · « **Reply #1 on:** February 09, 2009, 03:51:26 PM »

To add to this. Just asking here. If you used the 20' turbine stator and rotor size and put a 10' propeller on it would you get more watts? Than if I had the smaller size stator and magnet rotor that's is on the 10' turbine.

Thanks Brian

halfcrazy · « **Reply #2 on:** February 09, 2009, 06:19:24 PM »

I would say not unless you either had very strong winds or the possibility of running the turbine threw a controller like the classic would allow one to make a more powerful alternator to go with the same size blades.

But for straight on battery charging i believe Dan has found about the best compromise with durability and output etc in his 10 foot design.

Flux · « **Reply #3 on:** February 10, 2009, 02:18:02 AM »

If you put the 20ft alternator on a 10ft machine it will crawl round and produce perhaps 200W in a gale. At best to get anything worthwhile at all you would need to run a 24v stator at 48v. Even then it will hit hard stall not much beyond cut in and you will have a fairly constant low output which changes little with the wind speed.

If you use a mppt converter then it is a whole different game and you would have the potential to extract most of the theoretical power from a 10ft machine probably up to 50 mph or more. I suspect you have 5kW capability and the main limitation would be noise from the prop in high winds.

Anyone planning to use the Classic or similar from the start would be advised to use a bigger alternator than the standard one for the 10 ft machine but not even I would go as big as the one for the 20ft machine al though it wouldn't hurt in any way except for tower size to hold the weight and the unnecessary extra cost. In terms of efficiency it would be brilliant.

If you don't intend going to electronic control then for cost effective results stick to the original design ( round magnet version for decent wind area)

If you have a specific need for water heating then the large alternator could work provided you halved the turns to deal with the increased prop speed. You would need a series line heater to drop the efficiency down to about 50% at full load. The battery charging performance could be better than the standard alternator as you can add more loss to get it better out of stall. There would be no stator heating problem as all the heat would go into the series resistor. To add sufficient resistance to get full benefit you would have to redesign the furling if you lived in an incredibly windy area although in most areas you may be able to absorb the extra power and hope that it furled eventually. You would be able to keep it going up to fairly high wind speeds.

Unless you know what you are doing you will waste time and money with this venture but done wisely it could be very successful although I would probably start with a 16ft sized alternator.

Flux

halfcrazy · « **Reply #4 on:** February 10, 2009, 04:06:32 AM »

Flux a bit of a thread hijack but it does pertain i suppose. on the 10 ft design like dans. if i wanted to build a new alternator what would you recommend for the Classic? i would have to do new metal work but i can do that.

So starting from a blank slate lets design an alternator that will work with controllers like the Classic i would think maybe somewhere in the middle of the 10ft design and dans 17ft design. and am i correct in assuming the tail would need to be Longer or heavier as well to offset the more powerful alternator? and what would happen in low winds? i would assume the classic would manipulate the turbine and we would still get the same power or more as we would have wound for a slightly higher voltage.

i agree it is nice to be able to use the lighter towers of the 10ft machines so i dont want to get carried away. i just want to try to maximize the output safely. and see a good experiment at the same time

Flux · « **Reply #5 on:** February 10, 2009, 08:24:41 AM »

I haven't looked into this so take this as inspired guesswork at present.

The 10ft design with round magnets is likely not too far from the mark especially if the disc size was increased to use those magnets properly. The 12 rectangular magnets are way short of the mark. There would be many magnet options and at present I haven't looked in detail. Many are nice but few are cost effective, most likely still cheaper to use more of the rectangular blocks with at least 16 of them.

The 17ft alternator is possibly perfect for efficiency, I need to look at it closer. Remember the 10ft is way faster than the 17ft so you can virtually halve the turns and have 1/4 the resistance of the 17ft machine so in terms of cost effectiveness it is probably over the top.

Some increase in weight will be inevitable but I can't go with this idea of the tail balancing the alternator weight, it makes some sense in normal running but when it furls the whole thing goes by the wayside so the tower just has to handle some out of balance ( likely tiny compared with other stresses). Furling will need a complete rethink once you get away from stall control. From the furling point of view and for safety against tower strike with higher gyro forces from the faster prop I would bring the alternator forward ( probably significantly). No harm tilting it up a bit as well.

For direct connection you can't use a full load efficiency much over 50%. Letting the volts rise with a converter it may already be coming up to near 70%. With conventional rectifiers it seems difficult to get efficiencies up into the 90% plus region that seems possible for the alternator on resistive load so I suspect aiming for a full load alternator efficiency of 80% could be a good compromise. On most sites the very high powers will be so infrequent that it won't matter if your top limit is 4kW or 5Kw in terms of energy capture. As long as the thing doesn't cook its stator then anything over 3kW continuous output is about as good as you need. All these combinations will give you significantly higher energy capture in the 12- 20 mph winds where the conventional machine is half bogged down in stall.

Flux

trumpets3u · « **Reply #6 on:** February 10, 2009, 02:47:26 PM »

Wouldn't be smart for me running a mppt controller to wire the turbine to 48v and knock it down to my 24v batteries. And also to run the 3 phase from the turbine to the house than convert it over, or do you have to at the base of the tower, I'll be about 200-300 feet from the house.

Thanks Brian

halfcrazy · « **Reply #7 on:** February 10, 2009, 03:50:15 PM »

Brian i would say run the 3 phase to the house. now this is for a few reasons but if you went with say Midnite solar's Classic and there Clipper then you would want the 3 phase as the clipper has its own rectifiers inside. my turbine is 220 ft from the batterys and it is 70ish ft up the tower and i dont seem to suffer any il effects from the distance i did upgrade to #8thhn from tower base to the house. My turbine cuts in at 6mph and makes 30ish watts. then it climbs from there.

now for the voltage if you are going to use a controller like the classic then i would say wind it for 48 volts but if you want to go straight battery charging then you would want to wind for 24 volt.

Personnely i would design the turbine to take advantage of the Mppt controller and go that route but i may be biased. that said feel free to stop by and see it work someday if you want and you can check out the tilt up tower.

trumpets3u · « **Reply #8 on:** February 10, 2009, 04:12:58 PM »

Thanks for the input. I'm tiring to get my ducks in a roll here before I start. Where did you get your Midnight controller? Or is the Outback as good, That's what is on my solar.

Thanks Brian

halfcrazy · « **Reply #9 on:** February 10, 2009, 04:28:18 PM »

my Midnite controller is one of the first beta units but they will be available soon keep an eye out here and check out www.midnitesolar.com.

as far as the outback for wind it is not going to be any where near the value of the classic which will have the ability to have a custom curve for your particular turbine so you can keep the blades in there sweet spot basically it is designed for this job and it will also commuicate with the clipper if used which i recommend "cheap insurance".

halfcrazy · « **Reply #10 on:** February 10, 2009, 07:16:08 PM »

Flux am i right in thinking the round magnets should be spaced about the same amount as the magnet is itself? and if so would you use the same coils in the stator and just space them to match the mags? i may just have to start welding and ordering mags but i want to try to get the ideal design first.

Flux · « **Reply #11 on:** February 11, 2009, 01:44:13 AM »

Yes spacing the same as magnet diameter or just under. If you do that then you can keep the coil holes similar but you have space to wind a lot more copper until the coils touch. That is where you gain, you have thicker copper for the same number of turns. Don't keep the same coils and space them out.

Flux

halfcrazy · « **Reply #12 on:** February 11, 2009, 04:16:16 AM »

ok i think i am on the right track i will most likely start a new thread and try to get the ideal turbine design going you have been a big help flux. as i have really hijacked brians thread here

sorry Brian

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