| T O P I C R E V I E W |
| windnovice |
Posted - 05/04/2008 : 21:05:27
hello got wind members,
I am working on building my first wind turbine and i want to get the right motor for my application. I am aiming to keep the price for the turbine low so i am looking for a cheap motor that works well.
I hear a lot of good things about ametek motors and i would like to get one but i would like to look for a cheaper alternative.
I have been looking at treadmill motors and am thinking that those would be a likely substitute but i want some opinions on what motors other people have used and had success with.
Any help would be greatly appreciated!
Thanks,
Windnovice |
| 15 L A T E S T R E P L I E S (Newest First) |
| gotwind |
Posted - 12/04/2008 : 19:48:41
Thanks Ghurd.
A drill press is also known as pillar drill here in the U.K anyway, alternativly a lathe could be used.
Ben
The Futures Green - Getwind of it. |
| ghurd |
Posted - 12/04/2008 : 19:24:29
Sure is. But I'm not that smart. 
Don't push a lot past 18A, and it should be OK. HaHa.
They often won't go to 18A (or name plate rating) anyway. That's more like my luck. Some will go past double the name plate amps.
Some crazy things start happening at high RPMs.
The coil's inductive reactance can come into play. The brush losses change (I think). Eddy currents in the core. Stuff like that. Coil resistance (DC) is still important.
More important is the duty cycle, at the rated power. Heat builds up (the example needs a fan((the flywheel))). Windmills make power when it's windy, blowing away heat, meaning the amps can be pushed a little more than expected.
Enough of that.
130V/18A= 7.2 ohms. That's the best guess at the resistance. (Ohm's Law)
325RPM is 13V. 650RPM must be about 26V?
26V - 13V(bat) = 13V "extra".
13V "extra" voltage / 7.2 ohms = 1.8A. (Kirchoff's Law)
One step more, 975RPM... , ...= 3.6A.
Insult to injury? Treadmill motors are rated very strange. They may have a couple voltages, amps, HPs, and RPMs on the tag.
IE: Motor in the link.
130V and 2.5HP? 1HP=746W. 2.5x746= 1865W. 1865W / 130V= 14.3A.
130V and 18A. 130x18= 2340W. 2340W/746= 3.1 HP.
2.5HP and 18A. (2.5x746)/18= 103.6V
So what IS correct? Is it 14.3A or 18A? Is it 2.5HP or 3.1HP? 130V or 103V?
I don't know.
The inductance comes into play. A LOT.
Higher RPM = more reactive component. I have a feeling the higher the name plate RPM, the more it comes into play, but I can't prove it.
It's not very practicle to calculate inductance unless you already have the motor. If you already have the motor, connect it to a drill press (I can't recall what that's called in English-English)and battery and measure the amps at different speeds. Quicker, easier, and more accurate.
Most of that math doesn't hold up in real life, with a windmill, in my experience.
It sometimes seems we are using these motors at a very low RPM and voltage, compared to what they were designed for, and that helps a lot.
Fungus might be able to explain it better. My typing finger is tired.
G-
(PS- G., shoot me an email, G-)
|
| gholt |
Posted - 12/04/2008 : 17:46:48
Hello All,
Having read the great posts by ghurd and BushWhacker I took a look at this motor:
http://www.surpluscenter.com/item.asp?UID=2008041210081930&item=10-2190&catname=
2.5 HP 130 VDC MOTOR 3250 RPM
Draws 18 Amps
The calculations according to their respective posts:
13 (charging voltage)/130 (motor voltage) * 3250 = 325 rpm to reach charging voltage.
My question is ... Is there a method to determine the potential amperage available from a motor (at whatever parameters are required) ?
Thanks,
G. |
| windnovice |
Posted - 11/04/2008 : 04:50:17
Thanks for all your help ghurd and Bushwaker every little bit of knowledge helps =)
now i have a good basis for finding the right motor for my turbine!
Thanks!
|
| BushWhacker |
Posted - 10/04/2008 : 21:12:39
Hi Mr. Novice;
The way to work that out is Motor RPM divided by Motor voltage = RPM per Volt. Multiply by 13 (volts) and that is the speed it has to turn to start charging a 12 volt battery.
RPM/Voltage x 13 = charging 12 volts
your example would be 2600/24= 108.3 rpm per volt x 13 = 1408.3 rpm to charge a 12 volt battery.
Cheers!
BW
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein |
| ghurd |
Posted - 10/04/2008 : 21:06:12
Sorry.
Need to figure the volts per RPM. Or V/RPM. Then RPM at the voltage you want to get.
So the Schwinn motor is 24V / 2600 RPM, = 0.00923 volts per RPM.
A 12V system needs 13V to charge a low battery. 13V divided by 0.00923 volts per RPM = 1408.3 RPM before a 12V battery will be charging.
And that is if you are lucky. Usually it is higher RPMs.
Smaller motors may never reach 12V. Usually it is smaller motors that don't reach 12V. Larger motors get close to the math.
One more try...
(motor volts) divided by (battery volts) multiplied by (motor RPM) = (when that motor reaches 12V).
That means it may charge a battery at 0.001 watts.
Power comes after the RPM is reached.
The RPM should never be reached before 6 MPH. I aim for 7 or 8 MPH.
There is no power available below 6 MPH.
"TSR" is something to look into. Not much to worry about quite yet, but it won't be long before it is very important.
G- |
| windnovice |
Posted - 10/04/2008 : 20:03:26
thanks for the help ghurd
it seems like the more i get into building this project the more complicated it gets =)
i am curious as to what equation you are using to figure out the RPM there, you kinda confused me
with the (motor volts) part.
thanks
|
| ghurd |
Posted - 10/04/2008 : 16:31:29
RPMs are way too high.
Why.
13V to charge a 12V system. 13/24(motor V) x 2600RPM = 1400. It would need to spin 1400ROM to charge a battery.
Say the treadmill motor was 5100RPM and 130V. 13/130 x 5100 = 510RPM. And that's too fast, but better than 1400. |
| windnovice |
Posted - 10/04/2008 : 06:13:22
http://cgi.ebay.com/Schwinn-350W-Clutch-24v-Bike-DC-Electric-Scooter-Motor_W0QQitemZ110240837069QQihZ001QQcategoryZ11332QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
this motor i found on ebay says it has a centrifugal clutch and only engages when the motor is energized.
Just curious if this motor will work or not for a wind turbine, not sure if the clutch would have an effect on the motor.
thanks |
| BushWhacker |
Posted - 10/04/2008 : 04:11:32
Windnovice;
get it in a message and print it off is all I have to say.
Cheers!
BW
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein |
| windnovice |
Posted - 09/04/2008 : 17:43:28
yea i messaged the guy that had the motor about what the rpm's are like.
but i have not gotten a response back from him at this point in time.
Im thinking they are around 2000 or so, b/c thats what i have seen with other
motors of the same type. |
| ghurd |
Posted - 09/04/2008 : 15:30:49
I think he just doesn't know the RPMs.
Looks like he tells everything shown on the tag.
G-
(PS: G- is Not Greg) |
| BushWhacker |
Posted - 09/04/2008 : 03:34:42
Ghurd beat me to it with exception of proximity. If that is some wild 5400 rpm motor... eh ... not such a good bet, unless you have super secret 12,000 rpm blades, and lots of insurance to go with them.
I wish you luck but the seller seems to be a bit elusive concerning RPM.
Cheers,
BW
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein |
| ghurd |
Posted - 08/04/2008 : 20:03:35
I would be a bit concerned about the RPM rating. I can't tell if the RPMs are stated, but I can't see it on the tag.
Some/most are over 5000RPM at 130VDC, and they are not very good for a wind turbine.
5000RMP at 220 or 260VDC isn't so bad.
The US treadmill motors are not usually the same as UK types.
US types tend to be a bit cheezy. UK look better made.
Ameteks are well made, even if they are overpriced.
That said,
I spend more than that on stepper motors I'm pretty sure won't work.
And that link is only about 60 miles from me. I might just out bid you. 
Not really, I have plenty.
G-
|
| MattM |
Posted - 08/04/2008 : 13:45:57
I set my ebay bot to raise the final bid 1 penny at 4/10ths of a second before the end of the auction. I'll let you know how it works! :)
/just kidding
Go Huskers! |
