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Forum Index : Windmills : line resistors-makes a difference
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hi Glenn, and crew Looks like you did a good job and the hub "offsets' look strong. Sorry to hear about your prevailing winds , I've got a similar problem. I've only been settled here for 3 years and really in that time ,I'm convinced weather patterns and winds have changed. We remember gale force winds when we first moved in and have seen our 4 piece aluminium patio chairs and table actually get lifted and fly the length of the balcony. That's the reason I went full steam ahead and built the 50 foot tower ,. I've got the 11 foot Oregon blades up on the F&P and it turns continually now with the non-cogging rotor,24/7. So there's light at the end of the tunnel. Yesterday , I'm watching it and the control metres ,thinking,"something is not quite right here", so I connected 2 x 2 Ohm heavy wire wound resitors and connected them in series with the dc feed ,1 leg. Immediately the volt meter went off scale @ 60+ volts while the Amp clamp meter reached 3.8 Amps. It quickly settled back to .5 Amp and sat around 0-1 amp most of the time. Now remember,I can actually count the rpm at these low Amp readings ,approx 60rpm,I quess, and remember there stuff all wind. So, I'm now waiting for a strong wind to get some real results. plus fiddling around with different re-configurations. I'd try your blades if we can get them to Brissie easily. ps, this was a reply to glenn's post about his Chinese blades, but it's sort of a different subject ,so I made it a new post. Bruce Bushboy |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
Hey Bruce Yes a series resistor can make a difference. Its something I've wanted to play around with, but never got the time. The resistor lets the windmill run closer to its best blade speed for the wind speed. The F&P is a very efficient alternator, over 95%, so once a windmill reaches charging voltage in light winds, the F&P acts like a speed brake, keeping the turbine speed at charging speed. The blades work best at their optimal angle of attact ( 5 odd degree ). If the wind picks up slightly, the blades start to stall, and therefore dont make as much power as they could. It takes a lot more wind to overcome this braking and get the blades working at their best angle of attack, which is when the amp meter suddenly starts to go up. By adding a series resistor, you reduce the efficiency of the F&P as a speed brake, so the turbine spinns up easier over charging speed. It means the blades can run at their best angle of attack. Yes some power is lost in the series resistor, but the over all gain is more as we have a faster spinning windmill making more power. For light wind area's, this is a good idea. It also means the voltage drop over the power feed cable isnt as important as we once thought, its acting as our series resistor. But that said, if you have a lot of wind, you dont need the series resistor as the windmill easily gets over the charging voltage. Tell me that made sense? With the modified Chinese blades, I'm looking for someone who can compare them against a standard set of chinese blades. I need to know if the modifications have cut back noise and improved performance. On my F&P they did work well, for the few times the wind was coming from a good direction, but this tells me nothing unless I can compare them to another set of those blades. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hi Glenn. Yes, you explained it very well, and the way I have it connected ,it works exactly as you are describing. My observation is that if you are in a light wind area (hardly any wind)then you are not going to see much more than 30 watts occasionally going to 60 watts ,. The encouraging aspect of these non-cogging rotors is the fact that the mill will turn almost all the time,whereas before I could wait for a week before seeing any movement. I've just completed a new stator into 6 groups of 2 coils in series giving me .8 Ohm. I'm looking forward to see what this does .( the 6 groups of 4 coils in series ,5.5 Ohms gave me next to nothing o/p.) Good thinking on the chinese blades --maybe Ross is your best shot ,he knows about them. Bruce Bushboy |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
I'd be more than happy to test them for you Glenn. I have used (got) a set of the 3m (dia) blades that I've reworked and made a big difference to, but have SPL measurements before and after (as well as my own memories of them!) Could pull the blades of my own and try your hub, if the shafts are compatible, or erect another mast and put up my F&P. Have my own weatherstation so can compare against windspeed etc. Biggest downside would be freight... I'm as far south as you can get in NSW, right on the Vic border. Happy to help, would understand if you decline! |
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Trev Guru Joined: 15/07/2006 Location: AustraliaPosts: 676 |
Glenn's modified Chinese Blades.........I'll pay the freight down to Ross,if someone else will pay the freight back. I would really like Ross to test them. Ross would give us an honest report. All else fails, I would be happy to buy a complete chinese wind gen for some testing purposes. With my 2 towers beside each other we could compare. I would prefer for Ross to test them though. Trev @ drivebynature.com |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
Hi Ross and Trev Thanks for the offers. What I need to do is a swap comparison between a standard set and my modified set, so the windmill would need to be running the 1020mm blades already. I'm hoping someone out there already has one of the 200 watt Chinese windmills that they could try these blades on. If not, with I would like to try them on a F&P, somewhere that could log the results. With no winds up here for the next 6 months I cant do much testing. I'm trying to achieve two things. First up, here is how you can modify your blades on your Chinese windmill to make then quieter and give more power. And secondly, here is a cheap way to make some blades for your F&P windmill. Sorry to hijack your posting Bruce. How is that series resistor going? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hi Glenn. and crew. I had some definite improvement with the @ Ohm heavy wound resistor in series, but since then have taken the rig down and changed stators --yeppa, you guessed right , wind died . But when the wind was fair to mederate, I saw the mill gathering speed at the battery voltage level and that proved that it just needed that extra power in the wind to start charging--I used a clamp meter ,because the analogue meter was very hard to judge. Blades--well, I've had enough of these "no,low wind" days and biting the bullet,I asked Trev to build a set of bug 14 foot F/G blades for me ----- I know you'll all say "too big" ,,,but,,, I've got this feeling that with the larger blades I'll be able to drive the Neo conversion rotor and the geared transmission platform .... I'll see... During winter when the westerlies come in I'll be downsizing to my 11 footer ,and remember I'll have the disc brake working also. Catch up with you all in a couple weeks ---have a load of goodies to pick up in Sydney . bye for now Bruce Bushboy |
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