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Forum Index : Electronics : Pushing Amps
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robbo Regular Member  Joined: 25/03/2007 Location: AustraliaPosts: 71 |
Hey everyone,great to read all the threads, and know there is so many people interested in building these mills. They are beautiful things. But as it is is my first round, I seem to have a problem with my mill. I have setup in my small block in the Burbs, a 7p2p 7 Phase mill, (the best all rounder), probably not high enough off of the ground. I don't get a lot of wind here,but I do get gusty burst, for a few days, even up to a week at a time. So maybe I should of gone for the 48Volt system. Please advise. I have rectified the voltage on the mill, and drive the DC volts down to my Oatley K241 regulator, into a Dicky Smith, 20 Amps panel display, voltmeter, and then into the Battery. My problem is, when my mill hits 12.4 volts (or anything above the actual battery voltage), the ammeter only starts to flicker, and the mill then dies slowly. Maybe I don't have enough wind to push it past here, I dont know. The biggest I have seen on the Ammeter is about 3 amps, and only for a second.javascript:AddSmileyIcon('  ')
I am sure someone has had this experience before ? "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi robbo, As a start, I would temporarily disconnect the regulator. The mill should produce amps. Rotor speed may be limited by the battery load, but should not slow down as the wind is increasing. This eliminates a fault in the regulator setup. cheers, Gordon. become more energy aware |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
Do I take out the regulator, and let the mill spin over 12 volts, then measure the amps ? (ampmeter in place) I am using old car 12V Lead acids. They have been watched over a few weeks to see if they hold their voltage, and two batt do. Are these suitable until I can get better SLA's. Thanks for the reply. "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5012 |
Hi Robbo The old car battteries are fine to get started with. Dont expect much life from them, consider them a step up to a better battery bank. I used a car battery for about 2 years before finally buying some deep cycle batteries. It almost sounds like your windmill turbine isn't making enough power to drive the F&P over charging voltage. Either the turbine is too small, or there isn't enough wind. Can you give us more info about your turbine? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
The mill is the 7 Phase, 2 pole F&P as per the Backshed website. I have four "thin" blades on it. I went for four blades, for a quicker startup, but only had 6 inch PVC pipe. I now have a larger 12 inch pipe piece available, that I hope will produce a broader "root" part of the blade for better capture. It being a larger diameter pipe, will protrude less (horizontally), from the blade hub, so will produce less wind resistance when spinning. This will be a 3 blade model. I think this might help? Another Question with the amps. The amps only start to show when the voltage is at Battery level, is this normal ? 
 "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
Have bypassed the regulator, and found the amps only push after hitting the battery voltage, same as before. It still only pushes 1 to 2 amps.
(Had a diode inline as well, so there would still be some voltage dropping. I assume there should be more amps than this. It does push up the battery voltage though, although very slowly. I am thinking maybe I should of picked the 7phase 6pole for slower mills. Then I would have to find a 48 volt regulator. DO you know of any ? as cheap as the Oatley brand ? 
Sorry about the large Pics... "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5012 |
Hi Robbo Yeah your turbine is a little small, and those blades a too thin to make any more than a couple of amps. A bigger turbine made from 12inch pipe will be a big improvement. Also you need to get some height, thats a little close to the ground to work properly, not to mention it could take someone's eye out
Yes its normal to not see any charging current until your mill is making more voltage than the battery voltage. This is what we call the cut in voltage/RPM. Basically your windmill is free wheeling until it reaches this cut in RPM, and then it gets loaded. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi robbo, I assume you have the 48pole rotor with the 7phase rewire. What you describe is the way a typical windmill works when connected to a battery. Current can only flow when the generated voltage is greater than the battery voltage, unless you have a power maximizing cct that can extract power from the windmill at lower generated voltages like I have on my windmill. From your photos? How high above the ground is the mill head? The blades could be becoming stalled at the RPM when the load comes on. Do the blades become a blur if the load is disconnected temporarily during a wind gust? There are many possible ways a windmill does not produce power. From the location you are setting up your windmill, safety would be a priority. Some of the simple tests will require unloading of the mill head. High rotor RPM could eventuate for brief periods. If overRPM damage could occur, then this restricts the testing. good luck with your testing. cheers, Gordon. become more energy aware |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
Hi Glenn/ Gordon. I forgot to mention, that the picture wasn't the site where I have positioned my mill. Its off the ground about 5-6 meters. That pic was just to test unit. Sorry about that. I have open-circuited the wires, and the unit spins out to about 30 Volts, easy. Plenty of wind still ? This is in frequent burst, so I believe there is enough. I am thinking bigger blades again. Would wider blades and less of them produce a faster mill, and if so, will this produce more amps ? Or, do I not need a faster mill, but go right back to the core for a 24 or 48 V system ? Rob. Thanks for your time again (I don't know how you do it answering everyones problems, and keeping positive). "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
Note, Furling system is pretty bad, dont try this method. Will change on the next mill. "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi robbo, rule of thumb says half of open cct voltage gives close to optimum loaded mill voltage. The blades would appear to be stalling at the cut in RPM. cheers, Gordon. become more energy aware |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
Ok, so this means, I need the mill to spin faster (less blades) This would produce more current, at higher rpm's. then I can "push more amps". Yes ? Does a wider blade, or thinner blade help spin faster. I was under the presumption that thinner blades produced less wind resistance ? Is this right ? "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5012 |
Not so much spin faster, but make more power. Whats happening is your turbine cant make much power, so when it reaches cut in RPM it doesn't have the torque to get past that. Example, a 50cc motor and a 500 cc motor, both can spin fast, but when the load is applied the more powerfull motor will continue to accelerate. Yes a wider blade will help. More surface area. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Until you come up with wider blades, try adding a few washers under the hub to pack it out a little. This will reduce the currently excessive loading for those blades and allow them to pick up revs. You may be surprised at the results. The beauty is that there is nothing to hack off or weld on to give it a try and it helps you better understand and optimise your system. Similar to micro hydro for which this method is used to match and optimise smaller jets when flow rates reduce, so to it will get your existing system running quickly. Try 2 first up then add single washers thereafter. Once you get that gen load curve to stop intersecting the wind power curve it will stop stalling at around the 1/3 rev mark, then it will rev right up to max. Yes, power will be a fraction less than it's max power potential , but as Glenn says, you need wider blades for the power to get past this point to achieve that.  was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
OK, will build some wider blades, and get back to you if any more problems. Great Guys, thanks very much for your help. Your both a wealth of info. Thanks for your time.  "the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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| robbo Regular Member Joined: 25/03/2007 Location: AustraliaPosts: 71 |
Hey everyone, just to follow up. Have added wider blades from 12 Inch PVC, and all seems to be going well. Have seen more than 10 amps here on the new blades. (3 blade prop). Popped a 10 amp fuse one day, and that was a stupid move, all it did was open circuit, -but this gives a testimony to the strenght of my build -NO BLADE DESTRUCTION !. Very happy with it, all I need now is more wind. 
"the Earth was not given to us, by our fathers, rather, it is lent to us by our children". |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5012 |
Hi Robbo Great to see you got it sorted. Its a nice looking windmill, its making amps, what more could you want? 
And I bet you learned a lot along the way. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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