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Forum Index : Windmills : The ’skinny’ on my Ametecks
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scurrie Newbie  Joined: 29/04/2009 Location: United StatesPosts: 4 |
arial3blue I'm an Advisor for a High School Club called TeamGreen and we've undertaken a project to research, source, construct and install a 400W +/- Wind Power Generator to power the sign out on our front lawn. We've already done a fair amount of work on the project but still have some key problems to address. We've purchased a 38V and 20V Ametek PM motor and are wondering which of the two would be better to use for our project. The 38V is rather small, only 5"lx4"dia. and seems a bit small. The 20V is 7"Lx4"Dia. and weighs half again as much as the 38V unit. The Ametek's were the PMM's most suggested for use. Which would be the best choice for nominal low to medium wind conditions? Thanks scott the potter |
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DaViD Senior Member  Joined: 14/01/2009 Location: United StatesPosts: 120 |
Hi scurrie, I dont know anything about the Ametek motors but if they were mine i would chuck them in a drill or lathe with a known r.p.m. and check the open voltage at diffrent speeds to see what I was working with  If your not living on the edge your taking up to much space! |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Hi Scott Davids right, you need to spin them up so see what voltage you get for what RPM. As a rule the higher voltage motor would work better, but I feel even the 38v motor wont be any good for your windmill, sorry to say. And those motors are only good for 50 or so watts when used as a windmill, so you would need another 8 windmills to reach 400 watts. A permanent magnet treadmill motor is a better choice, I have a couple rated at 130v, so they reach charging voltage earlier than a lower voltage motor, and they are good for 100 or so watts. But I need to spin them at over 300rpm just to reach 12v, so I would need to use a smaller diameter turbine. Smaller turbine equals higher RPM, but less power. If you want to go over 100 watts, you can either convert an induction motor, use a big servo motor, a F&P if you can find one, or build your alternator from scratch. Its easy enough to do, and would be a good project for students. Check out http://www.otherpower.com for information on this, its an american site and very popular. Let us know how you go. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| scurrie Newbie Joined: 29/04/2009 Location: United StatesPosts: 4 |
Dear David and Glenn, Thanks so much for your council to 'rev' and measure my Motors. I knew to do that but did'ent do it largely because I don't have access to an easily measurable rotating machine. I do have a variable speed 1/2" drive electric drill which I can count rev's on and will do that later today. The larger question I have about all this is: Is there a common sense way of knowing what is the best relationship of motor horse power, motor voltage (tag rating), physical size & weight, Motor RPM (is lower RPMS better than Higher tag rated RPMS for lower wind power generation?) and amps> Watts for one to look to when deciding what is the best choice for a PM motor to use on a small wind turbine? Ours has an 8' dia. rotor. Thanks for anything you can offer that will rein in the variables I've seen in motor offerings for wind power on the web. scott the potter |
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| DaViD Senior Member Joined: 14/01/2009 Location: United StatesPosts: 120 |
Sorry Scott not enough info. to tell you what you need, like what kind of bulbs in the sign, what wattage, any ballasts, how far the windmill will be from the sign just to name a very, very few things. It's like Glenn said I would build my mill from scratch if I were you. Try here if you want free plans If your not living on the edge your taking up to much space! |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Scott, the current is the important number. This determines the heat that the frame has to dissipate. If the nameplate says 8.1A, and you want to use 12V system, then the power would be 97W maximum. For a 24V system the power would be double, but the alternator would need to spin at twice the rpm. An 8foot mill would spin at around an upper 500rpm mark. A typical treadmill motor would be rated 1500rpm, 120VDC, 8A say. This motor as a generator would be approx 150rpm for 12V cutin. approx 300rpm for 8A, so would work as a windmill for 12V system. Furling would need to be set to limit the max current produced to 8A or burnout will occur. Max power output would be higher as a 24V system, with reduced power at lower windspeeds. Furling would still be set to limit current to 8A. If you know the windspeed distribution at the site, then this will allow you to work out the best furling settings. No point in having a windmill output settings maxed out for wind energy that may occur for a few hours a couple of times a year. Testing maximum limits has a place in a laboratory, but better to have realistic limits set conservatively in you application. Gordon. become more energy aware |
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| scurrie Newbie Joined: 29/04/2009 Location: United StatesPosts: 4 |
Dear Gordon and David, Yes! We'd love to build our own axial flux generator per Hugh Piggot and will most certainly take that on as part of next years projects. However, we are now trying to demonstrate to our school and community that alternative power is not just a nice thing to do for the planet but can be done locally with the resources at hand in the school and community. Several seniors on our team are doing their senior projects as part of this effort. It's been quite amazing to see so many doors open up for us as we bump and stumble our way though this process of making alternative energy. Gordon, I appreciate what you wrote in response to my query. What I'm still needing to know, as the school year winds it's way down, is can we generate enough 12V electricity to charge a battery bank with the 20V Ametec Motor we have currently (pun not intended!).It will be located about 50 feet from the sign This stored DC energy will be inverted through a grid tie to supplement the 2.5 to 3.5 KW/month power requirements of three 4' long florescent tube backlights and a LED sign. Since this is a Wind and Solar project 60 watts of solar voltaics will also be in the mix. Thanks for your thoughts and suggestions. I'll get back to you about the spin-up results with the 20V motor. Scott scott the potter |
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| DaViD Senior Member Joined: 14/01/2009 Location: United StatesPosts: 120 |
Hi Scott, Yes that motor will charge a 12v battery bank and if everything else is right. 
A nor-easter should spin it up really nice at your location  If your not living on the edge your taking up to much space! |
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