Lakota Help

[Rock]

I have a 48VDC Lakota.  In the past few months I have had NUMEROUS wind events of 40 to 50 mph sustained with 70 mph gust, for days at a time.  IE HIGH WIND WARNINGS.

Problem is that the lakota only puts out 200 to 300 watts continuious at these wind speeds.  Every once in a while I will see 800 to 900 watts for a couple of seconds.

Even in sustained 20 to 30 mph winds I only see 200 to 300 watts.  

Question: When I installed the unit I used 2/0 copper welding wire.  Voltage drop at 1000 watts is less than 1VAC.  I am wondering if maybe I made a mistake doing that and I should have more resistance in the line in order to allow the wind turbine to spin faster before meeting resistance.  

It wants to furl in 20-25 mph wind conditions.  

Do you think output would increase by adding resistance??

If so how much resistance should I add?

Thanks

[Flux]

I have absolutely no experience of the Lakota but I believe the blades perform best at a high speed, you may be holding it into stall. You could try about 2 ohms and see what happens. With their alternator it may not help, I just don't have any data to work from.

I seem to remember it is a small machine ( 7ft ?). At even 25 mph you are not going to see enormous power so if it is furling at 20-25 mph you may not be far off the mark.

Possibly you may be causing it to furl early with very low line resistance so adding the 2 ohms may affect this even if it doesn't help the alternator.

I think they claim something like 900W at 25 mph, if so the thing must be matched at 25 mph and you may be holding it down. I think you will be very lucky indeed to exceed 600W at 25mph.

Those that see bigger outputs probably have machines that furl at higher than 25 mph.

See what the resistor does, but I doubt that a commercial alternator will have enough expensive magnets to hold it into stall at 25 mph.

Flux

[zubbly]

hi Rock,

i have no experience with the Lakota, but if i remember correctly, their furling is basically a tilt back design.  i am just wondering if the spring tention on it is not tight enough, allowing it to tilt back too soon.

maybe Jerry will chime in here, i think he is a lokota dealer.

hope ya get the problem solved.

zubbly

[Rock]

It's the high wind model and blades have a 6 foot diameter on that model. It also has a pretty good controller that has a 2000 watt diversion load too.  Right now I have the diversion set at 60 VDC.  This is because I have OutBack Grid Tie inverters that sell all power above 52VDC.  

Where should I put the resistor?  On AC side or DC side of Controller.  If I put resistor on DC side it could bump DC voltage up high enough to activate the dump before getting to the batteries.  I suppose AC side would be best but I do not know who to add resistance to a 3 phase line??  Short of just adding 50 feet of 14/2 wire to wind turbine output.  

Any advise would be greatly appriciated.

[Flux]

This all gets complicated with a controller that we know nothing about, if you want to try resistors keep them on the ac side so that it just looks like line resistance.

Anyway I think you have answered your question, you say it is a high wind model with 6ft prop, then what you are getting is about right for furling at 20-25 mph. If it is a high wind version then it will need to furl at well over 25 mph to get the sort of output you are expecting.

Try the resistors first if you want, that may affect the furling if there is a wind seeking force from the blades at higher speed, if that doesn't do the trick look at the furling as Zubbly suggested.

I suspect the peaks up to 900W you see are when the furling is caught out. 600W at 25mph from 6ft is close to Betz.

Flux

[Rock]

Any suggestions on what type and capacity of resistors I will need.  Each leg carries a max of 10 amps.

[Jerry]

Hi Rock.

I'm the Lakota dealer Zubbly is refuring to. My first expierience with flying a Lakota is simular to what you are expiriencing.

It seemed to stall it took alot of wind to get it to go. The Lakota has several wireing scheems depending on your available wind speed.

Low, medium and high speed conection are changed just inside a juction box where the big black cable enters the yaw area. Check your manual and set it for high wind speed. I allway use the high wind speed conection no matter what.

Forget the resistors. The Lakota is rated at 900 watts at 28.8 MPH. Here are some test #s I got. This was truck wind testing.

10 mph 63 watts,  15 mph 260 watts, 20 mph 420 watts, 25 mph 900 watts.

While flying on my store roof during some 40 mph wind I was seeing over 2500 watts coming from my Lakota.

Another thing to check. Ocasionally there is a slight missalignment problem with the brushes/slip rings. While flying in some mild wind measure the open voltage between all 3 phase it shold be very close.

I prefure to do this with 3 very cheap Harbor Freight meters. If you see some diferance you may have a slip ring problem.

I'll say again don't waist the power your Lakota is capable of doing by placeing resistors in cicut.

Thats kind like using the E-brake and keeping your foot hard on the gas at the same time to slow the car down.

Good luck and let us know what you find.

                        JK TAS Jerry

[Rock]

When I ordered the unit I was told to purchase the small diameter (6') because of my location.  Plus the unit was ordered in Mod 0, which I confirmed prior to installing.  

Will try to check open voltage ASAP but this time of year I rarely see winds less than 20 mph.  

I hate to say it but if there is something wrong with my slip rings the unit will be scrapped.

I have had some bearing problems and CHINA says they are sending a new upper unit for me.  That was last October.  I still have no upper unit and its quite possible the bearing is causing the low output but I cannot hear any noise from it.  Just a little play that China said was not right.  I personally do not think the bearing is an issue or I would have said something here.  I do not feel any more resistance in the unit than the day I put it up.  And the unit has survived 70+ MPH winds and keeps on turning.  I just think that in 40 or 50 mph winds I should be making more than 200 watts.

I think china is trying to troubleshoot my low output by replacing everything (Upper unit).  Problem is that its been 5 months since they said they would help me and still nothing.  

If its the slip rings than the upper unit will not help me and it could be another 1/2 of a year to get things right.  As of today I have owned the unit for about 11 months.  Do the math on how good my service has been.  

[Warrior]

Hi Rock,

I hope you get your problem sorted, but if you decide to scrap the thing do you mind taking it apart and posting pictures of the stator & rotor?

I've always wanted to get a look at it's guts...

Thanks,

Warrior

[Rock]

I can definately post photos of the inards.  Blades are good and I can probably sell them.  Controller is good to and I could probably sell it.

I can do the photos reguardless of wither I scrap or not.  If my replacement upper unit comes in I will take old one appart and post photos.  

[Jerry]

Hi Rock.

Have you e-mailed Lex at Aeromag? Hes helped me sort out some problems.

                       JK TAS Jerry

[Warrior]

Hi Rock, thanks. I'm looking forward to seeing those pics.

Cheers,

Warrior