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Forum Index : Electronics : 80P and RPM power dropoff
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| dazz Regular Member  Joined: 15/04/2008 Location: Posts: 78 |
Hi all, When you have an 80P config, the grphs tells us that the output watts drop to 0 at around 500RPM. Does anybody know why it drops off so quickly? It just amazes me that you can have so many coils wizzing round past magnets at 500RPM and get 0W out Where does the mechanical energy go in this situation? Just converted to heat? cheers, Daryl |
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Gill Senior Member  Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Sorry dazz, you say the graph is for a 80p, but where do I find it to check out what you say? Please give link or address. Thanks. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| dazz Regular Member Joined: 15/04/2008 Location: Posts: 78 |
Hi Gill, Sure, http://www.sustainability.ofm.uwa.edu.au/__data/page/83884/F P.pdf page 8 |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5012 |
Thats a well presented document, never seen it before. Its funny how many people are working on these F&P motors without being aware of eachother. The 500 RPM starting point for the 80P is its cut in voltage. Those graphs originate from EcoInovation and Michael did his testing into battery loads. To put it simply, the 80P didn't reach the cut in speed ( charging voltage ) until it hit 500 RPM. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| dazz Regular Member Joined: 15/04/2008 Location: Posts: 78 |
ahh ok, that makes sense. thanks yeh, it's great to have so many people working on different aspects of the whole. Glenn, have you seen any performance graphs for resistive loads? cheers, Daryl |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi dazz, resistive loads are very difficult to supply with a windmill. The blades will tend to stall, with the resistance calculated for the output voltage and power level expected... Gordon. become more energy aware |
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| dazz Regular Member Joined: 15/04/2008 Location: Posts: 78 |
ahhh ok  ta
Forgive me, i'm very new to windmills and how people get the most out of them. So I've been thinking about what Gizmo said about the EcoInovation test setup, and how there is no measurement below the cut in speed. Is it true to say then, that if the system was 48v and the speed dropped to supplying 24V then there could still be significant power to charge a 24V system if you could somehow flick a switch so that the generator was supplying a 24V system? Cheers, Daryl |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
G'day dazz, Yes that is correct. If you switch from a 48v battery load to a 24v battery load, current will flow through it when it is below cut-in voltage on the 48v battery. I am making a duel rotor system that incorporates a feature for using this normally unavailable power. Yet to see if the trouble is worth the added complexity. You may like to correct an error in the address above by removing the space between the 'F' and the 'P' in the file name.(only you and the administrator can edit errors from your post). These little glitches occur from time to time.... comes with the word computer.  was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| dazz Regular Member Joined: 15/04/2008 Location: Posts: 78 |
i've tried editing it several times and it just goes back to having a space. very odd Is the dual rotor specifically to have one drive a 24V system, or will your 24V feature be driven from both rotors? cheers, Daryl |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
The link was pretty easy to find from the parent address. If the cut-in windspeed is above 4m/s then there is a useful part of the normal wind energy spectrum that is potentially wasted.. Gordon. PS: If the cup anemometer of my weather station is moving, then my windmill is usually spinning, but the cut in I have still set at 2m/s. This only equates to about 100-200mA @ 24V. It will be interesting to compare the 100S F&P to my design when I finally get it set up.. become more energy aware |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Are you using the 'EDIT' button at the bottom of the post? If so, most odd. Without going into to much detail, When the voltage drops below cut-in, the two gens get switched from parallel to a series connection bringing the charge voltage back up above cut-in. Whilst you mentioned using one generator to charge two separate batteries, I'll be charging one battery from two generators, but utilising the same untapped power below the usual cut-in. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| dazz Regular Member Joined: 15/04/2008 Location: Posts: 78 |
i did use the edit button. i tried deleting the space. Also tried cutting the whole thing, correcting and pasting back. Thanks guys for the food for thought Daryl |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Gill, There may be some problems with the control this way with the state of charge of the battery. You probably should use a current sensing as well. The enabling of the series connection would be a current drop to zero. As the current rose to a predetermined amount then the parallel conection would be enabled. There may need to be some timing delays as well. A star/delta changeover could be incorporated as well on each mill in a similar way. The changeover could be then input power related. your thoughts... Gordon. become more energy aware |
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