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Forum Index : Windmills : Blade size
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| maaca Newbie  Joined: 21/11/2006 Location: New ZealandPosts: 22 |
Hi guys, I have picked up a small pm motor 3phase around 30 volts at approx 600 rpm.Im told 2amps. This will be my first and I want to do this one before I do a F&P later next year. I happened to have a three bladed prop at 650mm and adapted it to the motor.I then placed it in front of a large commercial fan and it wound up very nice but the cogging was an issue. I had to just turn it a fraction and away it went.The prop wasnt big enough to keep it turning under a load of 7 watts.{583m/a} I have two questions on matters I need help with. Would a bigger prop over come the starting problem with the cogging issue? and I obviously need a larger prop to acheive my two amps or 24watts output. Can someone help as to what size?. Perhaps 1.5 to 1.8 meters?.Many thanks. Maaca  |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Macca Yeah a bigger prop would be the first thing I would change. Not only would it help with the startup problem, you would also get more power. But dont go too big, bigger means less rpm. I would start with a 1.2 meter diameter blade. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| maaca Newbie Joined: 21/11/2006 Location: New ZealandPosts: 22 |
Hey Thanks Glen, Looking at the specs again,at 300 revs its just over 12volts. So I guess 350 - 400rpm would be good. I have to sort the starting problem out as the gen will be in a remote situation.Something like 20 minutes ride on a motorbike.So dont want to mount that thing and go up and start it up each day, or each gust of wind.May I ask you one more question. Would I be able to go just slightly larger with the prop size than 1.2m to make sure I overcome the starting problem with the cogging issue?.The gen is required to charge one 12volt battery for a radio repeater.If I was only charging 1-1 1/2 amps that would be fine.Total average draw off or load for the day is around one ampere-hour. From this you will see that two hours charging a day will be a huge help.Thanks again glenn. Maaca. |
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