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Forum Index : Windmills : What size amp meter?
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paul_mac1 Regular Member  Joined: 17/05/2010 Location: AustraliaPosts: 74 |
Hi Guys, Can someone please tell me what size amp mater I would need for my mill..... Its a 180v DC Treadmill motor, rated at 15amps and 2.2kw @ 4,000 rpm, obviously the won't get to 4,000rpm, more like 350 to 400 rpm, but what I want to know is will it still put out the rated amps? I admit, Im not an electrician....just a truck driver, who has built a mill, so any ideas on what size amp meter I would need, would be greatly apreciated. Does anyone know of any formula to work out the amps? Cheers, Paul |
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Greenbelt Guru  Joined: 11/01/2009 Location: United StatesPosts: 566 |
Paul_mac1, No, To get anything at all from this high speed motor you will have to overdrive it above your turbine speed. You have chosen 350 rpm as expected mill speed, this would be more than average wind. This is 5.8 rev's a second. The Ratio of rated speed to mill speed is 11.3 , If the rated voltage 180 is divided by 11.3 = 15.92 volts this is not an accurate way to figure it but gives a quick indication of what you can expect. you must also figure the rated amps will fall to about 1 or less. Your motor is not suited for a wind turbine. If you can find a motor with a rated speed of 8 to 1600 rpm. the coils in them are more compatible to Mills  Cheers----RoeTime has proven that I am blind to the Obvious, some of the above may be True? |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Paul Do not expect much from your mill as greenbelt says it is rated for higher revs but a 10 amp meter should suffice and i would expect about 5 amps to be a attainable power out put dependent on wind speed, you will need a set of high speed blades to get that however. 13 volt charging battery MS MPH TR_N TR-kg RPM Watts At Blade 0.5 1.1 0.1 0 67 0 1 2.2 0.4 0 134 0 1.5 3.4 0.9 0.1 201 1 2 4.5 1.7 0.2 268 1 2.5 5.6 2.6 0.3 334 3 3 6.7 3.8 0.4 401 5 3.5 7.8 5.1 0.5 468 7 Possible cut in speed 4 8.9 6.7 0.7 535 11 4.5 10.1 8.5 0.9 602 16 5 11.2 10.5 1.1 669 22 5.5 12.3 12.7 1.3 736 29 6 13.4 15.1 1.5 803 37 6.5 14.5 17.7 1.8 869 48 7 15.7 20.6 2.1 936 59 7.5 16.8 23.6 2.4 1003 73 8 17.9 26.9 2.7 1070 89 8.5 19 30.3 3.1 1137 106 9 20.1 34 3.5 1204 126 9.5 21.3 37.9 3.9 1271 149 10 22.4 42 4.3 1338 173 Possible 5 amp speed 11 24.6 50.8 5.2 1471 231 12 26.8 60.5 6.2 1605 299 13 29.1 71 7.2 1739 381 Possible 10 amp speed This is from altons wind calculator http://www.alton-moore.net/wind_calculations.php Have a look and you can see that it will need a blade of 60 inched approx 5 or six blades to provide torque to start and high rotation speed. You could use Philm blades as a three blades as they are high torque but may not go to higher speed needed for a reasonable output I haven't tried them at these speeds, It would be a good idea to make a drive up for it wit a stationary motor run it up and do some checks, be sure to load it as the dc voltage of this motor could be lethal if you come in contact with it. Hope this gives you some idea All the best Bob Foolin Around |
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GaryP Newbie  Joined: 01/06/2011 Location: AustraliaPosts: 15 |
Hi Paul, I have made a similar mill. My treadmill motor is rated at 4000rpm, 5amp, and 180v. It is lucky to produce 12 volts in stong winds and is intermittent at best. Apparently you need one that is is rated at lower rpm. these are generally hard to come by especially in Australia. It does work ok on a spin bike if you can get it up to 200 or more rpm but I can only get 1 amp out of it. Remember if you connect the amp meter it needs to be in series when loaded by your battery. Just putting the leads on in parallel is ok to measure voltage but not the amps. Cheers Gary $@#&*....the word often heard in my shed when it doesn't go to plan! |
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| paul_mac1 Regular Member Joined: 17/05/2010 Location: AustraliaPosts: 74 |
Hi Guys, Thanks for the replies, I have a 5 blade set of Windy Nation Turbo Torque Blades. I worked out that to get 14.4 volts out of it, it would need to spin at 320 rpm this is how I got to that conclusion: 4000rpm / 180v = 22.22 * 14.4volts = 319.968 so, 320rpm for round figures. But wasn't sure how to work out the amps. Thanks again. Paul |
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| GaryP Newbie Joined: 01/06/2011 Location: AustraliaPosts: 15 |
Hi Paul, I'm not expert but your calculations sound about right. My treadmill motor has the same specs as yours. Mine says it is a 5amp motor. I have one hooked up to a spin bike. See the photo. It is connected to 12 volt deep cycle batteries with a charge controller that keeps input at 12.4v approx and won't let it go higher no matter how fast it spins. I can tell you in practical terms what it puts out. To get it to generate 12 volts it needs to spin at minimum of 456rpm. My amp meter shows no amps or close to 0. To get it to generate 12 volts and get it up to 2 amps it needs a minimum of 720rpm. This is achievable on my bike because my cadence ie rpm of my pedals is usually 80. This gives me an rpm of the generator of 960rpm. ie 80x 3x4. ie 3 rotations of the bikes flywheel for every one at the pedals. The treadmill fly wheel spins 4 x for every 1 of the fly wheel. The minimum required to get to 2amps is 60rpm at my pedals. so 60x3x4 is 720rpm I know the amps because I have it connected permanently to the bike. So the moral is: This motor is no good for wind unless it is geared which ruins efficiency. ie I have never seen the wind blow this even at 35km hour winds fast enough to achieve 12 volts. Good for pedal bike but low amps. Better than nothing though. I am getting rid of this motor for wind purposes and am now working on an F&P post. See my postings for "F&P wont spin for 12 volt system" So you can learn from my wasted work....well I learned some things. 
$@#&*....the word often heard in my shed when it doesn't go to plan! |
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| paul_mac1 Regular Member Joined: 17/05/2010 Location: AustraliaPosts: 74 |
Thanks for your reply GaryP, Very interesting read.......might be looking for a new motor 
Bugger! |
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