dc permant mag motor questions

[nsargeant]

I am looking at a permanant magnet dc motor right now and have the following questions. First here are the specs on the motor

1 hp, 1725 rpm, 180vdc, and 5.3 amps

With this motor only drawing 5.3 amps, does that mean that that will be the highest amperage that it will ever charge a battery bank at? 
If thats the case than then this motor will never really produce even a 100 watts correct?

What is everyones overall consenus on using this as a wind generator?

I am pretty green to the wind energy community but I studied a little bit of it while in school.  I want to work my way into this industry and really get some hands on experience with developing a couple of windmills.

thanks,


Nathan

[zap]

5.3 amp at 180vdc is 954 watts... not that you'll get that much as an output but it's way more than 100 watts.

Did you possibly misplace the decimal point?

[nsargeant]

well I understand that but the motor will never be charging at 180v.  Somewhere in the range of 14-24vdc...
14v at 5.3 amps=72 watts
24vat 5.3 amps=127 watts

so just a little more than 100 watts

so in a perfect world is 127 watts all I expect to produce out of this or am I looking at this whole thing wrong.  Again i am a little new to this so bear with me.

I live in indiana so there isn't a whole lot of wind but there is a little bit.

Nathan

[rossw]

I am looking at a permanant magnet dc motor right now and have the following questions. First here are the specs on the motor

1 hp, 1725 rpm, 180vdc, and 5.3 amps

With this motor only drawing 5.3 amps, does that mean that that will be the highest amperage that it will ever charge a battery bank at? 
If thats the case than then this motor will never really produce even a 100 watts correct?

*IF* you just run it straight to the batteries, then yeah, around 5 amps is all you could expect.
However, if you have some way to trade volts-for-amps, you could see almost a 10-fold increase.
A "MPPT" controller is the usual solution here, but in principle, any DC-DC converter with an output at your battery charging voltage should do the job.
The caveats are of course, to watch how the mill performs. You don't want it un-loaded, so some sort of over-speed protection would be required.

[nsargeant]

ross if it isn't too much of a burden could you explain a little more in depth about how a charge controller would increase my charging capacities 10 fold or perhaps how it would work in this instance?

nathan

[rossw]

ross if it isn't too much of a burden could you explain a little more in depth about how a charge controller would increase my charging capacities 10 fold or perhaps how it would work in this instance?

Sure....

In a series circuit, the current is the same everywhere. So if you have a generator (your motor) that can produce 180V at 5 amps (900 watts), and you connect its output directly across a battery at 12V, the battery will limit the voltage output of the generator to "around" 14 volts while it's charging.

If your motor can only make 5 amps (safely - lets assume it has thin windings) - then thats all you can get out of it. (safely).

With a DC-DC converter, this is basically a switchmode power supply. It takes power in at whatever it can. It then has a high-frequency output stage that quickly turns on and off a device (usually a transistor of some variety - IGBT, FET, whatever). All that does is dumps charge into a coil. As the field in the coil collapses, it can supply quite high currents because of the very low resistances. Its this "low voltage, high current" transformation that helps you.

DC-DC converters are generally quite efficient - in the order of 85-95%, so you get out (lets say) 90% of the *POWER* you put in, in watts, at whatever VOLTAGE you choose to take it back out at.

So 5A/180V input (900W) * 90% = 810 watts out.
If your output is at 12V (battery is low and sucking up what it can), that would be 67.5 amps @ 12V. IE, more than 10 times the current you "could have" taken from the generator without potentially burning up its windings.

Make sense?

[ghurd]

Or basically meaning the generator (motor) outputs a higher voltage at less amps,
then the MPPT converts the "extra" voltage into more charging amps.

Ross' was a more complete answer.
I had a feeling you might have a hard time comprehending it.
G-

[rossw]

I had a feeling you might have a hard time comprehending it.

Yeah....ok, put another way, it's the same sort of thing with a welder.
You can plug that in on a 20A circuit but weld with 100 amps....

[Flux]

Lets look at this realistically.

Roughly your motor is 1 volt/rpm and long term thermally it is limited to a bit over 5A, as you say you are limited to something like 70W at 12v or 140W at 24v. in real life you can push it to about 50% over this under normal wind conditions, thermally you may be able to push it even more as the duty cycle of wind is low. The commutator and brushes may be more of a limit than thermal if you want a reasonable life.

Now cut in is going to be something approaching 150 rpm at 12v or under 300 rpm at 24v. As it stands the cut in speed is too low for a sensible size of prop at that power rating so you will end up with a very slow small prop with small energy capture or larger prop than you can likely control in any serious wind.

At 24v a fast 6ft prop will manage the cut in speed and will give you the 200 or so watts you can handle in a reasonable wind and you should be able to furl this safely. This would be a practical machine if you think it worth building something rated at about 200W.

Now the dc voltage converter, the the information is correct, you can trade volts for amps so you are no longer limited to 5 plus A.

The issue is now speed, if we look at the 24v case, cutting in just under 300 rpm, the fastest you could reasonably expect from a fast 6ft prop is a bit over 1000 rpm ( that's noisy). so you are up to near 100v. your converter in theory could raise your 5A to 15 or so A. In reality the internal resistance of that motor will be fairly high and I have a suspicion that the real life effect will be that your input volts to the converter will be nearer 50v, giving a 2:1 boost with the converter.  As I already implied you can probably push the motor short term to 100% overload the output with the converter will be quite similar to running direct. ( you are giving the motor an easier life with the converter).

If you charge directly with the converter at 12v you can now use the same size prop and get a similar output to the 24v case. You do gain in the 12v case.

To get a real benefit from the converter you need a transmission to run the motor up to its full rated speed or a bit more at your rated wind speed. You can now get the full motor rated power ( 1 hp) and you can use blades big enough to get this power in your wind speed.

Now the reality, if you are an electronics expert with an understanding of dc converters and you have the ability to build a mill with a speed increasing transmission you can build something with a rated power of a nominal 1kW at 12 , 24, or 48v.

If you are not an electronics expert or can't manage a larger mill with a transmission I suggest you are better off with a direct drive fast prop about 6ft diameter directly coupled to a 24v system and be content with 200W absolute peak ( furl long term below 200w). Accept that it will perform worse at any other voltage.

I have built mills with transmissions and mills with electronic converters, both have their challenges. My personal view is that for such a small machine the transmission is never worth the effort and if you must do it use a roller chain, gears and timing belts are a pain.

The dc converter if properly applied with mppt is excellent but won't suit your motor without a transmission.

If you are new to this you will have to do a bit of reading to understand all this, if you want a simple life your initial assumptions are in fact correct but so are the other comments as long as you understand the full implications.

Flux

[nsargeant]

Ross, Ghurd, and Flux,

I thank you guys for your quick replies.  I apologize if my questions seemed rather elementary.  My conclusion is that to use that motor and to get the power out of it that I would like, the cost/benefit is just not there.  The MPPT converters seem like pretty dandy pieces of equipment but that would come later on in my experiments.  Seeing that appropiate ametek motors are hard to come by and are pricey as well,  i guess that I am going to have to try to find treadmill motors to experiment with.  One thing that I was thinking about was possibly running 2 treadmill motors geared up to 2.5 or even 3:1 driven by 4' blades or even bigger if needed.  I would perhaps have them sitting side by side with a shaft driven my blades up above.  I know I would have to then deal with frictional losses but do you think the added gain of having another generator turning would be worthwhile?  What is your guys general consenus on this idea?

thanks again,

Nathan

[Flux]

No need for an apology, your question was perfectly sensible.

I think I should elaborate a bit on your comments just to make sure you haven't got the wrong ideas about wind power.

If you have found something to convince you that you can get a genuine rating from amteks and 4 ft blades that would justify doing things that your proposed motor can't then I am afraid you have been misled by a lot of hype.

Small wind power is fun as a hobby and can work on suitable sites under the right conditions depending on the need but no way is it going to supply major needs. I regard Amteks as fun starter things to get a bit of power to learn about wind power or to supply small needs on remote sites where no other power is available. the energy capture from a 4 ft machine on a normal site is tiny and only makes sense where it is the only source of power and the need is minimal.

The peak power from an Amtek in a storm can be quite high but you will be running the thing beyond any sensible limits and the average power will still be trivial, on many days a mere few watts.

Your proposed motor with a fast 6ft prop would give far more energy capture even if the absolute peak power in a gale was less impressive.

Don't kid yourself that those overpriced Amteks are going to solve something that your proposed motor won't. Amterks are a left over from a purpose that they no longer fulfill and were basicall worth scrap value until this hype all started. If you can't see any economic sense for your proposed motor than it will be foolish to spend a fortune on an Amtek.

A small machine of 4ft with any form of generator on a fairly normal site will probably average something well under 50W and that will be good. It may peak much higher for a few hours in storms but there will be many days when it produces nothing. Unless you have an exceptional site or can manage with a few tens of Wh per day then it is going to be a disappointment.

Small wind is fun for a hobby, it can supply a real need under certain conditions that could make life infinitely easier but other than that it becomes a very expensive source of power and sometimes there are cases where convenience outweighs nay cost factor.

I have seen some of the sites that you have probably been looking at and sadly they are far from reality.

I don't in any way want to stop you from having fun with wind power but I don't want you to spend money on false hopes .

Flux

[ghurd]

A  "GOOD"  treadmill motor is usually limited to about 100W in a standard set up.
Vast majority of treadmill motors are not 'good'.

I would suggest starting with the motor you have, in a normal direct drive 12V system with lower TSR blades.
There is no substitute for a bit of experience before going off the beaten path.

I said 12V because (usually) there are no small cheap and decent 24VDC to 120VAC 60Hz inverters available in the US.  They come in short lived bursts of availability, but it has been a long time since the last burst.
Not much you can do (cost effectively) with a small 24V system.
G-

[nsargeant]

flux,

I definitely not ready to give up on wind power yet.  For me it is just the beginning of a new hobby.  I am glad you guys are pointing me in the right direction because I certainly don't have the money to throw at a wrong decision.  The motor that I mentioned in my first post was one that I was looking at on eBay but haven't purchased yet.

ghurd,

I definitely see your point now in staying with 12v and not 24v after looking at some of the prices of 24v to 120vac converters.  I don't think i want to travel down that road quite yet.

My overall goal in this is that I want to be able to develop a cost effective solution to provide an alternative energy source to river cabins here an Indiana and elsewhere.  I would like to consider grid power as a "Plan B" or to just have it as a backup plan.  When we get out of this little recession that we are in now and my finances improve a bit I would like to buy some riverfront property and build a high efficiency cabin and "mainly" run on wind, solar and maybe a little hydro power if I could figure out a way to do so.

in the mean time I am just searching for the most practical motor to start building a wind turbine.

if you guys have any suggestions for  "good" motors that are readily available, i am open for suggestions.  The best compromise between potential power and money.

thanks,

nathan

[Rover]

Hi Nathan,

Based on your last post and your intent for a power source,

A lot of us do both solar and wind, have you looked at solar for your needs?

What is your site suited for?

 

[ghurd]

I had a great reply typed up, but Vista sucks, and IE10 sucks.
If the other window ever responds, maybe it will post.

"if you guys have any suggestions for  "good" motors that are readily available, i am open for suggestions."
The act of publicly suggesting makes it less available and more expensive.

Example.  
This whole treadmill motor fiasico may be my fault.
That $10 treadmill motor or legend.
260V McMillian.
The Surplus Center had thousands of them for many years.  Could not sell them for $10.
I posted it.
3 weeks later they were solad out.
A guy built a business reselling those motors.
Those motors sometimes sell on ebay for $300 now.
Is it a good motor to use for a windmill?
Yes, for $10.
No, not for $100.  Certainly not worth $300.

Is it a good motor?
For many years, they could not sell them for $10, if that says anything.
G-

[Flux]

Here 24 v inverters are easy to get, most suppliers offer both versions, so a 24v system is very practical and in many ways better than 12v.

If you are stuck with a 12v system then that motor is not going to be very good.

To be honest ( and I hinted at it previously) using dc motors is fine if they come at scrap price, which most should but once this hype takes over and they fetch silly prices I can't see any sense in going down that route. Spend your money on magnets and build a permanent magnet alternator and then you can build something that can be tailored to your needs and the long term results will be infinitely better.

I have seen wonderful machines built from top grade industrial dc servo motors and these were got for next to nothing. If you had to pay the list price for those servos from Inland Motor then it would be inconceivable to use them for wind power, they cost the earth.

Such things as Amteks and treadmill motors were available for scrap price until the ebay scam kicked in. They work well enough and can be really useful if the price is right but it isn't any more unless you drop lucky.

[nsargeant]

do you guys think the rpm is too low for this to be a practical generator?

http://www.motenergy.com/me0304012001.html

this is some additional info that I received from the company owner.

That is a totally enclosed motor.  It is rated at 22 amps continuous.  If it is spun at 320 rpm, you will get 3-phase AC at 36 Volts RMS.  It comes with a motor control, but you can remove the control to generate power.

The shaft is 7/8 inch. 

John Fiorenza
President
Motenergy, Inc.
3580 Slinger Road
 

[Flux]

There has been a fair bit of discussion here recently about using stepper motors for wind power.

I accept that they can have their uses for very small wind machines but personally I can see no future in trying to take this to a higher power level.

Steppers are designed for a totally different use and have so many characteristic that are against them for generating. With just a few exceptions, nearly any motor can be used as a generator but in general motors need very different characteristic from generators. I wouldn't risk any money on such a large stepper. Even if you can overcome the serious problem of cogging I still think the power you can extract from the high inductance windings will be very small.

If you must look for a motor rather then build an alternator your best choices are permanent magnet dc ones. The best of these will be very expensive servo motors but you may drop lucky and find one cheap. Failing that ac servo motors also work very well if you discard the control board. Similar in nature are brushless dc motors that are in reality pm synchronous motors driven by a control system. These are generally called ECM ( electronically commutated motor) and seem to be much more readily available in N America than here. There is not so much hype about them as Amteks and the price may be more reasonable.

Flux

[Rover]

If you are content with sub 200W output, can open a motor can, trace coil starts and stops, own a pair of small wire snips, and can join wires, then ECM's are not bad. But recognize what that means. If you have good wind, yep... it will work .. course if not (nothing will). You will need to read a bit on how to wire, rectify etc, depending on target voltage. Its a little more work than using a treadmill motor, but then again you don't have brushes to worry about and some of the other issues with treadmil motors.

These are 3 phase motors , 6 coils per phase, 18 coils total. For me  and 12V battery charging usage , I identify the coils in each phase, split the grouping so I have 2 sets of 3 coils per phase, parallel  the starts and stops of each 3 coil group, then rectify the phase. Basically this amounts to rather than having 6 coils in series per phase (as it is out of the box), you have 2 groups of 3 in series then paralled, which ends up dropping the voltage per RPM to a level more suitable for 12V.

Before any one slams me for span, I'm posting this as an assist. I have bought off this Ebay dude, I have one of these units (1hp ECM) , the best offer thingy is no joke , I made one, got it for what I thought was a fair price. As advertised they are new. I'm not affiliated nor trying to give this guy any business. That being said you may find other sources. GE ECM motors that work OK are in he 1/2 to 1HP range, but also look at the RPM mark.

http://cgi.ebay.com/GE-5SME39SL0988-1-HP-ECM-MOTOR-120-240-VOLT-1050-RPM-/200614843437?pt=LH_DefaultDomain_0&hash=item2eb593942d

If you go this route, feel free to post again, and some of us can give you some valuable instructions on how to do use it.

End of the day though, remember this is not going to get you oodles of power, 200W is a max mark, and you are looking at less than 5 ft mill (diameter).

I Hope this helps.

PS.. I have also used treadmill motors, my favority being a 2HP Baldor 90V/21A/2400RPM (not some unknown brand as you will find everywhere)... I lucked out on EBay with that one, Though I now use it as a variable speed motor (basically for testing other potential turbines). It did a stint here as a wind turbine, where it performed decently.