The Windtura 750 is now available - Questions?

Discussion in 'Windtura Generators' started by Minnesota, Nov 30, 2010.

  1. Minnesota

    Minnesota WindyNation Engineer

    Cool! ... urbine-kit

    I have a few questions:
    1. Is it identical to the 500 other than the PMA, and if so why such a price difference as the PMAs are only $100 different?
    2. Will all 750s come with a blue mount vs. black on the 500?
    3. Any plans to offer it with larger blades vs. the 500?
    4. What is the lead time?
  2. Minnesota

    Minnesota WindyNation Engineer

    A fun little Windtura 750 promo ... VID.
  3. murray2paddles

    murray2paddles WindyNation Engineer

    Windys test power curve results was using the three blades.
    I have been using the 5 blade for testing on a real time tower for a year & I am still convinced that it is able to produce more volts in the lower to mid range than the 3 blade.
    Now that I am using the new relay system built by Mark I am able to shut down home grid power on the 750 that is feeding grid ties and it is then feeding the same 12 v battery bank as the Windy 500 furling system test turbine.
    When the two are at full stop and the wind slowly picks up the 750 with it's 5 blades picks up well before the smaller 500 with 3 blades.
    I am very interested if Windy finds the time to do another truck test under similar weather conditions as their first run only this time using the 5 blades. My money is on a better showing in the low to mid range.

    I would also be interested in testing 100 inch blades on the 750.

  4. windyguru

    windyguru WindyNation Expert

    1. Is it identical to the 500 other than the PMA, and if so why such a price difference as the PMAs are only $100 different?

    When we intoduce new products, we like to offer them at a reduced, introductory price. This gives loyal customers who are familiar with our product development a chance to get a deal. The price on the 750 generator will increase.

    2. Will all 750s come with a blue mount vs. black on the 500?

    That is the plan. But, if someone wants a black mount for their 750, they can request one and get it for the same price.

    3. Any plans to offer it with larger blades vs. the 500?

    Larger blades spin slower. This will effect the cut-in wind speed, especially for 24 volt bank charging. Increasing the blade length could increase the cut-in wind speed to 10+ mph which would not be good. There is always a trade off.

    4. What is the lead time?

    We have them in stock. It usually takes us 1-2 days to ship an item out.

    Five blades could help a little with low wind conditions but I doubt it will help that much. If you look at the realistic power you can collect from a wind turbine with an 80 inch diameter rotor, the three WindGrabber blades seem to be doing a very good job. Additionally, if you take into account that the test results were collected using a test truck, the power readings are good. The truck does create turbulent air.
  5. murray2paddles

    murray2paddles WindyNation Engineer

    Careful now !

    Are you suggessting to the customer there is no need to purchase the 5 blade products because the 3 blade does a good enough job ? :twisted:

    On the furling for the 750 , did you center the mount pipe to the same location as the 500 ?

    Did you change the length or size of the tail or fin to allow a furl at 30 mph ?

    I hope my questions will provide answers on how you achieved balance on the mount as well as the furling.

    Blue, hmmmmm, maybe if you are from California :lol:

  6. Minnesota

    Minnesota WindyNation Engineer

  7. Barry

    Barry WindyNation Engineer

    Looking at your 750 watt and the charge controller, I was wondering where the brake is? I know that with my Whisper has a switch that shorts out the three wires from the generator making the permanent magnets act as a brake. Does the 750 have a brake?
  8. timber

    timber WindyNation Engineer

    Hi Barry,

    I don't have the 750, so take what I say with a grain of salt.
    I don't think there is a brake in the 750 kit but adding one would be very easy.
    Using a DPST switch is the least expensive switch to use to accomplish this.
    Here is a link to how to hook that up for a 3-phase turbine.

    All three legs of the 3-phase get shorted together using the DPST switch wired this way.
    Wish I had known this early on, I purchased a 3PDT switch which is much more expensive than a DPST switch.
  9. Minnesota

    Minnesota WindyNation Engineer

    Are there plans for Windtura 750 compatible preassembled charge controllers? The ones for the 500 are too small.
  10. TomT

    TomT WindyNation Engineer

    You have to go with the 100 amp charge controller for the 750 watt.
    The picture is wrong. Windy Nation needs to have it changed.
    The right picture is in the wiring diagram.


    Attached Files:

  11. Minnesota

    Minnesota WindyNation Engineer

    Ah, yes TomT, they do need to make this update. I was thinking of a preassembled one like advertised for the 500 with the bridge and divert loads.
  12. windyguru

    windyguru WindyNation Expert

    Yes, that is on its way. Too much to do and no time to do it.

    There will be a pre-assembled controller for the 750 as soon as we can get it done. In the mean time, one can use the 100 amp controller.

    We have started the initial design of a more high end controller which uses PWM charging, transistors instead of relays/solenoids, and will have an LCD screen for a simple set-up process of the controller. The LCD screen will read, in real-time, (1) Amps to the battery (2) voltage of the battery bank (3) Watts to the battery bank and (4) kWh produced. You can also use it to digitally set the charging/dump voltages.

    We are a solid year away from delivering this product.
  13. murray2paddles

    murray2paddles WindyNation Engineer

    Dear Mr Guru,
    On the furling for the 750, did you use the same mount as the 500 ?
    If so, at what location on the mount did you place the mount pipe to allow balance on the tower ?
    To have a furl at 30 mph, what did you change or add to the tail to create this increase ?
  14. windyguru

    windyguru WindyNation Expert

    Hi Murray,
    It is the same. We started out using a counter weight design to balance the 750 turbine. It worked just fine.

    Then we tried the 750 without changing anything. The weight increase was so small it had no effect once the turbine was mounted on the tower. The power readings were identical with and without the counter weight. Then we tested the 750 turbine by rigging it to rotate on a schedule 80 tower pipe. I wanted to make sure it did not wear the tower. It was fine.

    I was not that surprised. If you check out many of these home built Hugh Piggot 10 foot wind turbines, most of them are not perfectly balanced in the x and y direction (z being vertical) and they run for years and years and years.

    The furling wind speed seems to be identical for the 500 and 750. It might be 1-2 mph higher or lower for the 750 but it seems to be pretty much the same. If we had a very accurate way to test this, like a wind tunnel, we would know for sure. There are multiple variables changing here so it is difficult to pin point exactly what causes the furling to stay basically the same.
  15. murray2paddles

    murray2paddles WindyNation Engineer

    On the test mount I had moved the tower pipe forward to the front of the mount thinking I was compensating
    For the weight difference, I was also using a 5 blade on the 750 so I had thought that also would create a difference as well. The end result being they both furled perfectly only the 750 well before the 500. I have added 1.4 lbs to the 750 tail so I am now waiting for stronger winds to monitor at what wind speed it furls at now.
  16. windyguru

    windyguru WindyNation Expert


    I gave some thought to why your 5 blade 750 furls in lower wind conditions. If all other variables are held constant (tower offset, tail length, tail weight, blade length, etc etc), I think it comes down to the weight of your blade rotor.

    The five blade set weighs about two times the weight of the 3-blade rotor. The blade rotor is offset from the tower mast by a couple of inches. This creates a lever arm that makes the generator and blade rotor want to rotate around the tower when the blades are spinning. The tail is the opposing force which prevents the generator and blade rotor from rotating around the tower. The tail wants to remain parallel to the wind .... but ....

    when the blades get spinning fast enough in high winds, their momentum and the torque they create overpowers the opposing tail force. The blades and generator turn out of the wind and the tail stays into the wind and rotates "up" the 20 degree hinge.

    Momentum and torque both have a mass component in their respective equations. Because the 5 blade rotor weighs nearly twice as much it has nearly twice the momentum. This causes the 5 blade unit to furl in lower wind speeds (I am operating under the assumption that the blade rpm is relatively similar for the 3 blade and the 5 blade sets in the zero to 35 mph range. Of course the 3 blade will have a higher rpm but not twice as much compared to the 5 blade rotor.) So, my educated guess is that a heavier blade set will furl sooner if all other variables are held constant.
  17. murray2paddles

    murray2paddles WindyNation Engineer

    Ok, seems we are looking in the same direction. Not only did I have the extra weight of the mount and two more blades , but when I moved the mount pipe forward on the mount to balance out this also increased the forward leverage out even more.
    This will be important to know on the Windy 500, 3 vs the 5 blade on what mph furling may happen. The new blades arrived today so as soon as the cold let's up a bit I will do the change over on the next test. See good job I have that wind monitor now I will be able to monitor the mph on the 5 blade furling :D
    I was going to add some counter weight right away but now I won't . Will test this way first, record what happens & if required take it down again and then start adding weight. Will check with you first though if weight is needed to see where you would like it placed and how.

    Josh, you have been the greatest to work with, you and your staff have treated everyone with respect and honesty. It is because of that you ave earned All The Best In The New Year.
    Your friend,
  18. murray2paddles

    murray2paddles WindyNation Engineer

    A day later , on the first line I meant the extra weight of the rotor :roll:
  19. windyguru

    windyguru WindyNation Expert

    Thanks Murray. Happy New Year to you! I hope this is the year you install a 5 kW wind turbine!
  20. timber

    timber WindyNation Engineer

    Best wishes for you all in the new year!
    Glad I found Windy Nation and the forum, great people with similar interests.
    I still don't have my turbine in the air, I've been working at it as a hobby so it's all coming together, albeit in slow motion.
    This is going to be a great year. I'll be very interested in hearing more about the 750 not to mention the possibility of Murray's "5kW"!

    Great New Year to all!


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