17' flying - questionable output

[dlenox]

All,

Thanks to lots of info that I have acquired from the people on this site over the past year.

I have a 17' wind turbine that I finally got flying and spinning.  Here is the project url: http://www.briery.com/wind_turbine

This turbine is pretty close to the 'original' 17' that the OtherPower.com guys made. Here are basic specs: 48 volt, rotors have 16 - 1.5"x3"x3/4" N42 neo magnets per rotor (there are two 20" diameter rotors), stator has 12 coils with each col having approx 80 turns of #14 wire (about 1.5 lbs copper per coil), connected with 4 coils per phase.

There was a calm 6mph wind (at ground level) so I decided to 'spin' the turbine, I turned on all electronics, unshorted stator and removed the manual brake actuator.

In this low wind the turbine seemed to be spinning at about 60rpm, I could tell as the brake rotor had a 'squeak' to help keep timing.

When checking voltage across each of the 3 phases (I have no neutral) I was registering about 44 volts on my meter, and I am using a Sanrex DF150BA80 3-phase bridge rectifier to convert to DC.

But here is my question: I am registering no amps across the shunt, I would have expected something.

I realize that the wind speed may not enought to bring the turbine up to cut-in speed, but am curious about the 0 amps.  Tomorrow I have an backup Sanrex rectifier and will try it in the others place.

Any comments/suggestions?  I'm scratching my head.

Dan Lenox

[dbcollen]

44 vac should be 62 vdc after the rectifier, if your battery is connected to the dc side of the rectifier and below 62 volts you should be above cut in and some amps should be flowing.

If you meter is not true rms and the waveform from the alt is not a good sinewave you may be getting an erroneous reading and may not be at cut in yet. Also your shunt may be wired incorrectly.

Dustin

[snowcrow]

  There will not be any current flow until the output voltage of the turbine is higher than that of the battery bank.

Blessings, Snow Crow

[Flux]

You are cut in and there should be current. It may not be high enough to register on a large ammeter in low winds but it should be there.

Don't blame the rectifier, try a smaller ammeter in series with the other.

Flux

[tecker]

Sounds like you need to switch out the Xantrex and go to straight to the batteries to get a good read in to the load .I have to say with the control in there you haven't brought the bank up. The voltage is below cut . Put a charger on the batteries and see if the voltage follows the charger .

[tecker]

You may need to setup the Xantrex

[dlenox]

Ok cleared my head this am.

Again we have about a 5mph wind - you know it really is true that once you get a wind turbine spinning that you will not have wind!  And it is the same forecast for the next week!

Using my meter I checked the voltage from ground to each leg of the 3-phase output from the turbine and each was 24v, which should give me about 33v after the rectifier, so I do not appear to be at cutin speed.

I went back through all my settings on the Xantrex and everything appears to be set correctly.

I think that I may just have to let it wait for more wind...

Dan

[Flux]

That's one of the biggest limitations of wind turbines, they need wind.

You will certainly not be cut in at 24v ac. Usually below cut in the volts drift about, but become steady once your peak equals the battery volts.

Probably just as well you get nothing in a 5mph wind, if you make the cut in low enough to do so you will kill the performance above 10mph. Just be patient wind often goes away for several weeks but the damage is not permanent.

Flux

[DanB]

Hi Dave - interesting.  I am confused as to why you have 80 turns of 14 gage wire - is that a single strand?  Do you have an idea about what rpm you're seeing cut in speed?  I should think it's too low, and if you did wind with a single strand I should think the resistance is pretty high.  In my old 17' machine I think we used 59 turns w 2 strands of 15 gage in hand or something.  (its on the webpage anyhow).  More recent machines have fewer turns with 2 strands of 14 in hand for 48V.  

[DanB]

I was just reviewing my own pages on that.  So we used two strands of #14 in hand, 59 turns per coil for 48V in the later 17' turbines.  If you used a single strand/80 turns then your stator resistance is perhaps 5-6x more than ours which will cause problems.  We also built one for Rock, intended to be a 16' turbine and used 3 strands of 15 gage, and about 50 turns/coil.  His tower crashed and he's since replaced the blades w/17' blades and it seems to be working quite well.  I worry that your stator is not right...

[Flux]

He said that he had 44v ac at 60 rpm so that should be above cut in, so it will be below 60 rpm. I agree that it is low but in the present winds he doesn't seem to be cut in with 24v ac at a claimed 5mph.

The 60 rpm cut in seems to check fairly well for 80 turns using 12 coils. I find that #14 will go in with a stacking factor of only about 25% so he probably had room to have used thicker wire or 2 in hand. I agree that it is too slow and too high resistance but he has these things to face later when the wind picks up.

This is going to have to furl below 1500W to avoid frying but it will probably stall very badly so it may be controllable.I can only think that the wind is even less than he thinks, it ought to be doing something at 6mph with such low cut in.

Flux

[dlenox]

Flux,

The 44v that I previously stated was across 2 of the phases, later posting said 24v from one phase to ground.  My mistake with initial post.

Danb,

Yes I think that you are right about the stator, looks like another mistake on my end - I think I used the page where you made a test coil using single strand.  But later on you actually made coils with 2 in hand, 59 turns.

I have a sneaky suspicion that essentially I am stalled out.  The winds out here have been gusting to 15mph and not much difference in voltage output.

Other than rewinding the stator any suggestions? Although that may be my only recourse.

Dan

[dlenox]

Ok,

After thinking about my situation I think that there is no choice, and the lesser evil is to redo the stator.

Well this one was really good practice!  After all I have tons of climbing experience, I know that the davit crane and telescoping tower work, and all the components fit well.

I still have the original mold, it needs some work but that is where I will start, then re-wind coils (correctly this time) and recast stator.

Thanks again for all the help/advice but this one is a do-over!

Dan Lenox

[dlenox]

DanB,

Confusing day.

I looked back on my project pages and initially bought two 500' spools of #12 wire, and two 800' spools of #14 wire. My parts list page wrongly stated that I used #14 for the coils, however the ongoing project page said that I used #12.

I looked in my garage and found the spools of #14!

So initially I did make coils out of 80 turns of #12 (one in hand) and not #14.

Do you think that this changes anything? Or is the stator redo inevitable?

Dan

[Dave B]

Dan,

  I don't know what others think but I would open the air gap. It will raise the cut in RPM if you still want 48 Volts and with the right adjustment take you out of stall. Yes, you can duplicate what has been done before but you may also be able to be very happy with what you have with some adjusting. Your location, your blades, your load, your controller, your furling etc. etc. is unique to your build and location.

 Blades can change everything. To have the same performance as what the Dan's have done you would need to duplicate everything exact. It's possible you could have a very respectable set up of your own as is with adjustment. Maybe not the opinion of others here or even the best way to go but I have worked the variables for quite some time to tweak my own system which is unique also (direct heating). You can always wind another stator. Just my thoughts,  Dave B.

[Flux]

44v ac between a pair of rectifier terminals means that you are cut in. When you say 24V to ground that is pretty meaningless unless you have access to the star point.

Even with it well stalled you should still be getting a few amps at 15mph. If you still can't measure anything you have a measurement problem and you need to sort that before messing about with new stators.

If you by any chance have access to the 6 phase connections, try it in delta or Jerry connection and that should bring the cut in up to something reasonable. If not then try a big increase in air gap, get the speed up to a point where it at least comes out of stall in low winds and try some line resistance to get it up to a better speed in high winds.

The #12 wire is not too bad, it's not going to give the best results in high winds but it may do what you want and give good enough results in normal winds.

Just to prove things for now, drop off one rectifier lead, it will not stall single phased. If you still cant get current and the speed comes up you have other problems to sort before going off to build new stators. The thing is to collect as much information with what you have, before starting out on a rebuild.

I don't think you are so far off that it won't work, just keep investigating and sorting data. It must surely be doing 4A or so even hard stalled at 48v in a 15mph wind. I still am not convinced that you haven't got a measurement problem.

Flux

[tecker]

  With 520' of wire per phase your limited to 6 amps and I   don't think you'll be happy with 18 amps from that machine jerry  phased (If you coped out a neutral) . If you could cope out the interconnects you could mix and match single phase and have a respectable 50 plus amps in good wind . That's the only real option at 130 ' per coil.  The resistance is s probably the reason for low amperage you sinking the power through 1000 feet of wire that's with 600 360 degree turns you would want to derate the power starting at 200 feet.  

[tecker]

I see you may have used 12 That really isn't going to help much with the 3phase star the resistance is too great.

[Dave B]

  There are some proven guidelines to help design an efficient axial machine for battery charging. I am a firm believer in not re-inventing the wheel if you want to duplicate what has been documented. If that's what you are expecting for output and it's not the same then yes there seems to be something different from your set up from what you wanted to copy.

  Check your open volts each phase, are they the same say for 60 RPM ? (pretty easy to click off that count rather close) Be sure to be ready to short the output to slow /stop the alternator. Touble shoot from there so you are positive what you are working with before rectifying and adding the load. Again, your system may not be "bad" at all but just different from what you were expecting based on other's.

  If you have a sound 3 phase alternator outputting 3 seperate phases at approximately the same voltage per phase per rpm then I say learn what you do have and work with it before making any radical changes. There is no right or wrong if it works well for you. Keep us posted so we can all learn besides.  Dave B.  

[dlenox]

tecker,

I don't have 520' of wire per phase.  Currently there is 150' of #8 coming down the tower into my garage, from there I have 160' of #2 wire going to the rectifier in my basement (all copper).

Flux,

I don't have access to the star point, it is buried in the stator and I did not bring it out.  So all I have access to is the 3 phases at the rectifier.

Currently the air gap is about .080" on each side of the stator, between the stator surface and surface of magnets.  I see the battery voltage rising very slowly and suspect that essentially my wind turbine is not much more than a 'trickle charger', but do not know enough to trouble shoot to much of any degree.

DaveB,

I checked voltage between each of the 3-phases at the AC side of the rectifier and they are all pretty close, at about 60rpm I measure 44volts between each leg. I have a breaker between the rectifier and the DC distribution box, when opening it I see the voltage starting to climb, but can't observe the blade speed from my basement.

Schedule was very tight last fall and I was still building stuff the night before the tower was to be erected. Looks like stator details eluded me, but I must have suspected something otherwise I would not have had the spools of #14 wire, then time lapse through winter made me forget.

My original intent was to copy the older version of the 17' that was made, and I believe in duplicating good work especially in an area that I am not fluent in.

At this point I have made no decision on what to do, but am inclined to redo the stator per specs since this seems to be the one glaring error that I made.  Since I already have the copper wire, the only additional outlay is resin - and time.  So it seems like the most cost-effective thing that I can do.  Without the time crunch of last fall I can test/debug 'more better' prior to bringing up the tower.

Would love to learn more about what I have, I just don't have the time and knowledge. For now at least I am content with watching it, and will let it run to see if it shakes out any mechanical issues, and will monitor it.

Dan

[tecker]

 Add that 150 on total for for your stator  I looked at your web site .( tasty layout there )  you posted 6 coils at 800 feet for the stator I based the the lenght from that.

[ZooT]

Quote:

I see the battery voltage rising very slowly and suspect that essentially my wind turbine is not much more than a 'trickle charger',

You might want to define "very slowly".......because if you've got a large battery bank it'll take some time to bring the voltage up.....

[Flux]

"I checked voltage between each of the 3-phases at the AC side of the rectifier and they are all pretty close, at about 60rpm I measure 44volts between each leg. I have a breaker between the rectifier and the DC distribution box, when opening it I see the voltage starting to climb, but can't observe the blade speed from my basement."

If you open circuit the battery circuit at 13mph I would expect the voltage to at least double and very quickly ( seconds).

"Currently the air gap is about .080" on each side of the stator, between the stator surface and surface of magnets."  

Doesn't tell us anything as we don't know the stator thickness, air gap is from magnet to magnet.

 "I see the battery voltage rising very slowly and suspect that essentially my wind turbine is not much more than a 'trickle charger', but do not know enough to trouble shoot to much of any degree."

You shouldn't be using battery volts as a charge indicator, for some reason you seem unable to measure amps and you must sort that before doing anything else, you are just guessing without that information. You will not be able to do any worthwhile troubleshooting without measuring current. Measuring wind speed is bad enough and you could be way off on that one, but you must be able to measure current.

By all means go for the new stator, do it now if you like and change it when it is done, but at least learn form your present one otherwise the new one may still not solve your problem.

Fux

[wooferhound]

-quote-

"I have a breaker between the rectifier and the DC distribution box, when opening it I see the voltage starting to climb"

If you get high winds and the current gets high enough to Pop the breaker, then you will have an unloaded Mill overspeeding out of control in high winds.

[TomW]

I have to throw in with Flux here. without current measurements you cannot make a logical decision based on facts as they are. I have seen measurement errors throw even seasoned electronics folks.

Always check any measuring device before assuming the reading it gives is a sign of trouble. Lots of folks are thoroughly confused on how to make these measurements consistently and accurately. A simple blown meter fuse would show no amps even tho the potential for them is there but the open fuse prevents a circuit from being completed.

None of this is rocket science but understanding how to measure system performance is important. And it must be done properly to be useful.

I have trouble offering specific, detailed advice because there are so many things I don't even consciously think about and some are critical items.

Good luck with it.

Tom

[dlenox]

All,

Ok I finally got myself a relatively good meter and checked out some things.  I also put a wireless anemometer on the tower about 1/2 the way up, just over the tree line.  Today the wind is varying between 2-6 mph.

The blades startup with just a small gust of wind, about 2-3 mph and with some gusts of wind they are turning at about 90-100 rpm.  Measured voltage across each leg and getting about 40 volts.  My clamp ampmeter read about 1.2 amps on the DC side of the recifier block.

To reiterate: I have 12 coils, wound with #12 wire, 80 turns each, using a total of about 950' wire. From there I have 150' of #8 wire to garage, then 150' of #2 to the rectifier.

Resistance values:

    #12 : 1.5883 ohms per 1000'

     #8 : 0.6282 ohms per 1000'

     #2 : 0.1563 ohms per 1000'

Resistance for single phase:

      coils = 0.503 ohms

    #8 wire = 0.094 ohms

    #2 wire = 0.023 ohms

Total resistance per phase = 0.62 ohms

I then disconnected the wiring to the recitifier block and measured across each leg and got 1.3 ohms which would be the resistance of two of the phases, and it works out correctly.

So I believe that the result is, that my turbine cuts in at a very low speed and due to the resistance stalls out very early on.

DanB,

One question that I have is in winding coils, I am thinking that winding with 2 or 3 in hand using smaller diameter wire (even though their resistance is higher) that by 'paralleling' them this actually reduces their cumulative resistance.

Like if I had three 10 ohm resisters in parallel their total resistance is actually 3.33 ohms.

If this is correct then I believe that this is the reason that you typically use multiple in hand to wind coils?

Ok now I think that a light might have just gone on!

Dan

[dlenox]

DanB and All,

As many of you know I fashioned my 17' from the 'older' OtherPower design, and of course made a blunder in the coil winding of the stator in my 48 volt system.

I do not want to redo the rotors, but it seems pretty obvious at this time that I will need to redo the stator. DanB had previously mentioned in this thread that the 'older' design actually used 59 turns of #14 for the coils (2 in hand), DanB also mentioned that he made a stator using 50 turns of #15 (3 in hand) for Rock.

I know that my rotors are larger in diameter and could probably fit the 3/#15 coils and in about a week or so need to make a decision on which stator to make.

For those of you that are unfamiliar with my project I have two rotors (20" diameter) that each contain 16 - N42 1-2/2"x3"x3/4" magnets

Certainly would appreciate any recommendations and guidance on which way to go, my goal is to maximize the output with the blades/rotors that I already have. With my fixed tower arraignment putting up a new stator/turbine is no trivial matter and don't want to make another major mistake.

Second time is the charm...

Dan Lenox