Borderline wind speed

Discussion in 'Windtura Generators' started by Crayfish, Mar 21, 2010.

  1. Crayfish

    Crayfish WindyNation Engineer

    I am new to the forum and I have a question. I have a WN 500 PMA on a 32' tower on the back side of my property. It's clear of obstacles for at least 300' diameter around the tower. I am using a Flexcharge controller with (2) 120AH Trojan batteries. My blades are 1/8" aluminum, 30" long and have a 2.5" radius curve. I made them in the sheet metal shop at work.I am working on getting wiring to my house so I can eventually grid-tie but for now I am using it to charge batteries and use an inverter to run devices around the yard.

    My question is:
    When I have good wind 15-20 MPH or so I am getting 12-13 volts, the PMA is under heavy load and seems to be dragging. If I unhook the battery, the turbine spools up rather quickly and puts out over 100 open volts. Is there a way to electronically "slip the clutch" and keep the rpm's up to have the voltage stay at 14-15? I realize that the amps will go down (I am getting about 2-2.5 amps at 12-13 volts currently)

    Additionally, is it safe to stop the PMA by shorting two of the three wires? I would like to put a stop switch in but I want to make sure it will not damage the PMA.

    Any answers would be appreciated.

    Thanks in advance

  2. okiezeke

    okiezeke WindyNation Engineer

    There are two possibilities I'm aware of. One is that the PMA is overpowering the blades, that is, you need more blade to power the PMA. Longer, larger airfoil, more blades, or any combination of the three might help. Second is that the resistance of your diodes, charge controller, batteries, etc., does not match the PMA. This is not as likely to be the problem, but if trying other blades doesnt work, could try adding a resistor to the AC or DC line of the system. Try 10 ohm and see if it makes any difference.

    Good luck.
  3. okiezeke

    okiezeke WindyNation Engineer

    To answer your 2nd question. Every 3 phase AC machine I've seen uses the concept of shorting the output wires together to serve as a brake. Dont know what might happen if you shorted outputs downstream of the rectifier. Might irritate the rectifier???
  4. windyguru

    windyguru WindyNation Expert

    It is ok to short a 3-phase PMA after the rectifier by connecting the DC positive and negative wires. The only requirement is that the rectifier can hand the amps going through it. And if you are using an appropriately rated 3-phase rectifier, it should handle the amps with no problem.

    Also, I think your radius on your blades is not enough. Try going to a 4 inch radius and make the blades 35-40 inches long. And have the blades at least 6 inches wide at the base (before bending). If you do this, you will see a dramatic improvement in the performance of your PMA.
  5. Crayfish

    Crayfish WindyNation Engineer

    Thanks for the replies guys! I kind of knew that my blades might not be enough but it's sort of epic to lower my turbine so I was hoping for an easier solution. I will make another set and give it a whirl (no pun intended).

    So far I am very happy with the Windy Nation PMA, I just need to get everything in sync. I also may have buggered up my charge controller when I used light bulbs for my diversion load and they burned out and something shorted. I might be purchasing one of the WN controllers in the near future.

    Thanks again

  6. windyguru

    windyguru WindyNation Expert

    Light bulbs are absolutely no good as diversion loads for precisely the reason they failed on you. They burn up. There is a ton of misinformation on the internet which suggests that light bulbs are suitable diversion loads. This is unfortunate.

    Use two of our 300 Watt dump loads as your diversion load for your WN PMA (choose the 12V model for a 12 volt battery bank and the 24V model if you have a 24V battery bank).

    Your flex charge controller should still be under warranty. Just call or e-mail them and they will either repair it or replace it for free. A charge controller should not break just because the diversion load fails. So I would be firm with them on either fixing or replacing it.
  7. murray2paddles

    murray2paddles WindyNation Engineer

    when you said epic to lower your turbine. If you are interested I had some posts and pics in the photo section that shows how I raise / lower 32 ft towers with no problem. Takes about 5 min or less for one person. If you need more info drop me a line, will be happy to share with you.
  8. Crayfish

    Crayfish WindyNation Engineer

    Lowering my turbine is a bit of a pain, but I think at this point it's what I need to do. Murray2paddles I would like more info on your setup so when mine is down I can make some modifications to raise and lower easier next time. I found a short piece of 8" pipe at a friends ranch that I will make a die out of for making a new set of blades. Hopefully increasing the radius from 2.5 to 4 and the length from 30 to 36 will increase the efficiency and make the right voltage.

    I made another discovery, if I use new fully charged AGM batteries (6 of them 7AH each) from the PV/wind setup on my barn and put them on the WN PMA setup, I get plenty of voltage to charge (15-16 volts). The bigger batteries I am using on the 500 watt setup are old and may take too much current to charge them. I am going to switch battery banks today and see if that works before I take the turbine down. We are in the windy season here in Central Texas and I want to use this new power while it's available.

    I will post some pictures soon.

    Thanks again.

  9. murray2paddles

    murray2paddles WindyNation Engineer

    I will take some pics for you and include a short write up on them. Not sure if this section would allow all the photos so I will go to the photo section of the forum to share the info with you on the tower. Will just title it raising and lowering a 32ft tower.

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