Author Topic: newbie with a gift 400w wind generator  (Read 8249 times)

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KMac

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newbie with a gift 400w wind generator
« on: June 04, 2016, 08:11:27 AM »
My father-in-law bought a 400 watt Nature Power wind turbine for our little hunting cabin.  (http://www.naturepowerproducts.com/product-details.php?id=118).  I already have 1kw of solar panels with 315 amp/hours of Trojan batteries wired 24v there, which works great.  So I bought a 30 foot guyed tower and put it up in a nice spot (in the open on the prairie).  I ran wire from the turbine to battery box with 12 gauge wire as per the instructions. 

Now, this little turbine has a single box that accepts the 3 phase AC, and uses shorting of those lines as a brake for high winds, or if the batteries are full.  It also rectifies to DC and uses MPPT to charge, and says it will work with 12v or 24v systems.  I put that brake/controller at the end of the 220 foot run of 12 gauge wire. 

Well, it started, and it charged some.  It was able to brake in light winds with the shorting brake switch.  A high wind day came and it went into "protection mode" and burned up. After reading a bunch here (can't learn enough), I realize that: 1.) small wind turbines like this might not be ready for prime time; 2.) the instruction to use 12 gauge wire is ridiculous, particularly at 200+feet; 3.) the tower is too far away from the batteries for the wire gauge; 4.) the electrical brake is too far away from the tower. 

I already have the turbine (it was a gift and on warranty), and the tower up and well anchored.  I am not too concerned with how much it charges as I already have adequate solar charging, but it would be nice to at least have it up and running with the brake functioning so it will not burn up. 

So, if I am not going to change turbines (a gift), and moving the tower is not going to happen,  should I move the brake/charge controller from the batteries to directly under the tower?  Should I increase the gauge from tower to brake/controller to something hefty, and from the controller to the batteries to something adequate for voltage loss?  As noted above, I am a newbie with this, but that seems intuitively likely to improve my odds. 

Any thoughts/ideas will be appreciated. 
 

Mary B

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Re: newbie with a gift 400w wind generator
« Reply #1 on: June 04, 2016, 03:01:56 PM »
Put a brake switch at the base of the tower that shorts ALL three phases! If you are gone or know bad weather is approaching short it out to protect it. Putting the charge controller that far from the batteries will be an issue if you can't control the cut off voltage...

KMac

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Re: newbie with a gift 400w wind generator
« Reply #2 on: June 05, 2016, 02:25:26 AM »
Okay, I will put in a shorting switch brake at the base of the turbine. 

For when I am not there and it gets windy unexpectedly, the controller is supposed to short brake in overspend (1400 rpm) and over voltage.  Do you think I should move it closer to the tower?  I am afraid the too thin of wire over that distance makes the brake short ineffective?  Am I correct that the thin wire inhibits the effectiveness of the controller braking short?  If I increased the wire with a parallel run might that help too?

DamonHD

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Re: newbie with a gift 400w wind generator
« Reply #3 on: June 05, 2016, 03:23:27 AM »
You may be able to build (or buy) an automatic triac/SCR-based automatic crowbar or more gentle brake that goes at the base of the tower and is independent of anything else in your system.  For my tiny (50W) turbine I put it right next to the turbine with the battery around the other side of the house.  My brake was a rather unkind crowbar, but it didn't fire very often.

Rgds

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KMac

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Re: newbie with a gift 400w wind generator
« Reply #4 on: June 05, 2016, 09:20:37 AM »
Not sure I understand.  Are you saying that I do in fact need the electric braking mechanism at the base of the tower to work best?  And that I could build/buy one separate from the one in my controller which I should keep next to my batteries? 

I am still wondering if this is all just a function of too thin of wire over too great a distance to provide good braking.  If so, then buying/building a triac/SCR-based automatic brake would not be the simplest solution.  But if you think the wire is not the issue and I need it . . .

DamonHD

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Re: newbie with a gift 400w wind generator
« Reply #5 on: June 05, 2016, 09:28:41 AM »
If your feed wire back to the controller is (too) thin than having the emergency brake unit as close to the turbine (with as short a length of wire from the brake to the turbine) as possible will help.

FWIW, here was my unit, YMMV, and also I am no expert at all and my turbine was small and my winds tiny:

http://www.earth.org.uk/wind-power-pilot-autumn-2007-MotorWind.html#crowbar

Rgds

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KMac

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Re: newbie with a gift 400w wind generator
« Reply #6 on: June 05, 2016, 11:11:02 AM »
Damon, good write up and well-done!  I learned from it and I now get the use of the word "crowbar"- it could be a rough stop sometimes, like a crowbar in the spokes of a wheel, right?  We have things in common in that we consider our solar adequate but want a top-off from a wind turbine and as a complimentary charging source. 

Certain problems are evident from my off-the-shelf turbine kit (which I emphasize was a gift).  I think I should have the shorting brake near the turbine itself, and perhaps the rectifying mppt controller function should be located at or near the batteries. But they are together in one unit.  So, should I just put the whole thing at the tower and run the DC to the batteries?  Which is more important? 

I have read ChrisOlson posts that would suggest it is often best to have the rectifier at tower base and run the DC long run. He and Flux have had some great conversations I've learned a lot from, but think I might be missing some fundamental considerations in how I think of this situation.  Consequently I don't know for sure if I should move the unit, and whether the suggestion to put it at the base tower is complicated by the use of MPPT in the charge controller. 
« Last Edit: June 05, 2016, 11:30:08 AM by KMac »

KMac

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Re: newbie with a gift 400w wind generator
« Reply #7 on: June 05, 2016, 10:38:17 PM »
Well, I put in 6 AWG all the way, running 3 phase to the base of the tower (40 feet) where I put the mppt charge controller/rectifier that uses electric short braking to stop or slow the turbine when over speeding (1400 rpm) or when batteries are fully charged (28.6v).  From tower base it goes DC about 180 feet to the batteries.  My primary concern is maximizing the brake ability, and I am less concerned about watts lost.  But I do wonder if having the mppt charge controller that far away will work given it is supposed to detect  battery voltage and charge or shut down (short the AC side) accordingly.  Interesting design trying to pack it all in one. I just wish the shorting brake were separate from the controller.

Not muuch wind forecast for a few days so I won't know much for awhile. 
« Last Edit: June 06, 2016, 12:36:28 AM by KMac »

kitestrings

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Re: newbie with a gift 400w wind generator
« Reply #8 on: June 06, 2016, 12:54:52 PM »
It's pretty handy to have a brake switch at, or near the base of tower even if it is only to allow you to work on it.  Sounds like you've got it sorted out, but if you find the controller/rectifier is better protected inside, you can add a simple double-pole, double-throw switch and get all three leads sorted like this:



Good luck, ~ks

DamonHD

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Re: newbie with a gift 400w wind generator
« Reply #9 on: June 06, 2016, 12:57:21 PM »
Neat and efficient, ks!

Rgds

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KMac

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Re: newbie with a gift 400w wind generator
« Reply #10 on: June 06, 2016, 01:08:41 PM »
Yes!  I'll do that.  Great idea and interesting I can use a 2 pole to do it.  Thanks!

Not sure I've got it all worked out yet for certain, and may try moving the controller closer to batteries after awhile.  Need to see it is protected for now in strong winds with the bigger wire.  I just can't imagine why they said 12 gauge was enough, and  without talking about distance! 


DamonHD

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Re: newbie with a gift 400w wind generator
« Reply #11 on: June 06, 2016, 02:48:41 PM »
The charge controller (and inverter) should always be as close to the batteries as you can make them, with as fat cables as you can reasonably manage*, because of the currents involved, and in particular the charge controller's need to measure battery voltage accurately and not see confusing voltage drops which may result in your batteries being spoilt through over- or under- charge.

*I say this as someone who only very recently finally upgraded my controller-to-battery-bank wiring to something sensible...

Rgds

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midwoud1

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Re: newbie with a gift 400w wind generator
« Reply #12 on: June 06, 2016, 03:04:59 PM »
From Vdc to the Relay coil  you can make long wires.



Rgds.  FBM  Midwoud1

Adriaan Kragten

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Re: newbie with a gift 400w wind generator
« Reply #13 on: June 07, 2016, 04:25:18 AM »
Transport of DC current  requires 2/3 of the amount of copper for certain copper losses because for transfer of AC current, a wire in used only 2/3 of the time for star rectification (see my report KD 340). If you use a 3-phase generator rectified in star as brake, the braking torque is maximal if you make short-circuit in between the three phases and the star point. So you need a cable with four wires from the generator to the short-circuit switch which should be mounted at the tower foot. If the generator has no external star point, and if you therefore can short-circuit only the three phases, the maxiumum braking torque is only about 75 % of the braking torque with the star point short-circuited too (see measurements given in report KD 78). The higher breaking torque for short-circuit including the star point is caused by circulating higher harmonic currents in the winding. The 3-phase rectifier must be mounted directly after the rectifier, so also at the tower foot. From the rectifier, a long 2-phase wire goes to the battery charge controller and dump load and these components must be situated as close as possible to the battery to minimise the voltage drop in between the voltage controller and the battery.

KMac

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Re: newbie with a gift 400w wind generator
« Reply #14 on: June 07, 2016, 04:25:45 PM »
From Vdc to the Relay coil  you can make long wires.



Rgds.  FBM  Midwoud1

Sorry, as a newbie I just don't know what this means exactly.  Not trying to be obtuse, but does that mean I can run a long DC line from the rectifier/controller to my batteries? 

KMac

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Re: newbie with a gift 400w wind generator
« Reply #15 on: June 07, 2016, 05:10:54 PM »
Transport of DC current  requires 2/3 of the amount of copper for certain copper losses because for transfer of AC current, a wire in used only 2/3 of the time for star rectification (see my report KD 340). If you use a 3-phase generator rectified in star as brake, the braking torque is maximal if you make short-circuit in between the three phases and the star point. So you need a cable with four wires from the generator to the short-circuit switch which should be mounted at the tower foot. If the generator has no external star point, and if you therefore can short-circuit only the three phases, the maxiumum braking torque is only about 75 % of the braking torque with the star point short-circuited too (see measurements given in report KD 78). The higher breaking torque for short-circuit including the star point is caused by circulating higher harmonic currents in the winding. The 3-phase rectifier must be mounted directly after the rectifier, so also at the tower foot. From the rectifier, a long 2-phase wire goes to the battery charge controller and dump load and these components must be situated as close as possible to the battery to minimise the voltage drop in between the voltage controller and the battery.

Thanks very much!  The papers you have referenced are excellent. Here is what I gathered:  In terms of maximizing short brake, my turbine only has three wires so unfortunately no star braking (75% braking torque at best).  The rectifier is best at foot of tower so as to save on wire.  The charge controller is best near the batteries to minimize voltage loss. 

Here is my problem:  My 47 inch (1.2m) diameter turbine is 220 feet (67m) from my batteries.  My turbine came with all three functions contained in one box/unit: 1.) the over speed/over current shorting brake (and short switch); 2.) rectifier, and 3.) mppt charge controller are all in one box!  I can't separate them!   I can't go buy a new generator or controller at this point.   

So I am faced with a choice -  Where should I place that unit? 

The first setup I put the over speed brake/rectifier/charge controller unit near the batteries using 12AWG (3.3mm2) wire from the turbine the entire 220ft (67m). Everyone said the controller needed to be near the batteries, and that is my experience with solar.  It seemed all good until the wind got strong and the brake was too weak, and it burned up.  (I was following manufacturer's recommendation with that small wire gauge too, by the way - go figure!)

I was worried mostly about the over speed brake being too weak and burning it up again, and being unable to separate the brake from the rest of the unit (with rectifier/controller), I put teh unit at the foot of the tower thinking I am maximizing braking torque.  I also installed 6AWG wire (13.3mm2) from the generator to the unit (and from there to the batteries as well). 

One question is if the mppt controller function over that distance?  That is a major unknown.  I don't know if it will sense the voltage wrong in the battery at that distance and mess up  the output.  I suspect it will not work right.  If it isn't able to charge right at that distance, then I will have to move the unit to the batteries and hope the over speed short brake function will work at that distance from the turbine, now that I have thicker wire installed. 

So my questions are: 1.) whether, with an mppt controller, I can place it at a distance and it will nevertheless charge the batteries? And 2.)  If I have to make the choice to move the whole unit to the batteries, whether the shorting brake is likely to be sufficient at that distance, given the wire gauge now used? (e.g., how do I figure shorting torque over distance given a certain wire gauge?)

Any thoughts you might have as to the choices I can make with the equipment I have would be appreciated.



   

DamonHD

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Re: newbie with a gift 400w wind generator
« Reply #16 on: June 07, 2016, 06:12:17 PM »
If it were me, this is how I'd view it:

Keep the brake close to the turbine.  If necessary fit an extra one near the turbine and control it remotely or locally.  My crowbar didn't need any remote control for example.

Keep the controller close to the batteries.

The distance between the turbine and controller shouldn't hurt the MPPT function IMHO (maybe you may have to tweak settings a little), but an excessive length wastes energy heating the wires...  And I wouldn't sweat too much where the rectifier is, but note the potential slight extra losses with AC.

Rgds

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KMac

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Re: newbie with a gift 400w wind generator
« Reply #17 on: June 11, 2016, 05:50:52 PM »
Update - the turbine is up and running, and seems to be charging okay.  I had turned off my PV for a few days and it kept the batteries up, with a max battery voltage on the 24 v system at 28.69 v.  It is supposed to have a top voltage of 28.6 v at which point the system is to shut down via shorting brake.  I was not there but suspect that is exactly what happened. Because the regulator/controller is 170+ feet from the batteries, I suspect it was running pretty low current to them and was therefore fairly accurate in detecting the voltage to short break. 

It is less than ideal solution to place the controller 170+ feet from the batteries, but the shorting brake for over speed and over current are all in the same unit, and shorting torque is critical. I have 6 AWG wire and I suspect that helps quite a bit - going to run a third wire of it to the battery box in anticipation of possibly moving the entire unit there someday (don't think I'll ever get used to a controller that far from batteries, and even if it works will have to try it out).

KMac

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Re: newbie with a gift 400w wind generator
« Reply #18 on: June 19, 2016, 11:49:17 PM »
Still working. . . So far it appears to confirm that running the shorting brake at tower base, rectifying and then running DC the long run to the batteries isn't necessarily a bad idea.  Haven't made it through any monster winds yet though. 
« Last Edit: June 20, 2016, 03:50:59 PM by KMac »

KMac

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Re: newbie with a gift 400w wind generator
« Reply #19 on: July 13, 2016, 04:10:46 AM »
Still working through some healthy winds.  The unit is at tower base and the brake works, it rectifies and the charge controller works from that distance from batteries as well.  It kept the batteries powered up recently when my PV was down again.