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About kf

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  1. Well basically I have a program that just uses an equation to calculate the Coefficient of Power. And I can change the blade pitch as a value in the program and I can change the speed. I've read lots of ways of doing speed control, blade control or using both speed and blade control to get the best power achievable foe a given wind speed. The model actually works and that's all fine. I just dont get how in practice how one achives speed control when the blades are fixed. Basically when I google what I am doing, I get websites that dont go into detail because they are for novices, they just specify that you can control speed or pitch or both, and then I get papers that dont explain at all because they target audience of the papers is other engineers. So while I get how one could change the pitch to influence the speed, I dont know what they do for speed control. I have heard its done on the generator side but I have no idea what ideas are out there. is there a breaking mechanism they can use with brake pads? or can you adjust things on a generator so that it resists some of the torque coming from the rotor?
  2. How does one slow down the speed of a wind turbine to follow the maximum power point? I have modelled one and the speed is controlled but now that I think of it I dont actually know what the lads n lassies actually do on site to slow one down. I get that the blade pitch can be controlled and that of course that would just have actuators to turn the blades. But what do they do for speed control? just use break pads to slow it down? Can you use the generator to slow resist torque/speed? or even can one use the generator to speed up the wind turbine if it travels too slow. My model didnt need to go into that detail so I just have the torque being influenced to show that the power varies as the speed or blade pitch varies.
  3. for small wind turbines (domestic uses), do they only influence the Cp with controlling the tip speed ratio. And do nothing to the pitch? was just wondering. I assume at small levels that it becomes too expensive to put in a controller to and movable blades to allow that. AND, if anyone knows of any internet resources where the techniques are discussed how the TSR is controlled let me know of them? I've seen things that are too basic or too complicated. nothing in between.
  4. kf


    Anyone know any decent tutorials on control theory. I must model a windturbine. but just need something to help me go through the process of modelling it and then using the laplace transfrom so i can draw the block diagram. ANY tutorial. it doesnt have to be a windturbine. any device that was modelled. I've kind of learned it before and am trawling through old notes but i'd love to find something that just ran through the details of it to save time.
  5. kf


    traditionally the difference between 1 and 0 is represented by a change in voltage. but is it worth it to represent them with a difference in frequency? does anyone know where i can read about that? would it be more beneficial since you could have extra states? low frequency, a mid range and a high? similar to ternary but would it be easier with changing frequencies as opposed to different voltages? and perhaps even more states. i assume i'm not the first person to wonder this so can anyone point me in the direction where i can learn more about it?
  6. kf

    wind turbines

    ok. thanks for the replies. for the gears problem:each set of blades has its own gearbox and rotor. surely the different speeds would not be a problem.with a rotor and stator theres no problem with different speeds so i was thinking here would it not be the same. basically the stator is moving counter to the rotor(but since its moving its name is changed from stator to rotor) and yeah i see the other problems too and accept them. has it also been investigated and does anyone know where if this design is feasible. again the stator is moved so its two rotors. lets say one was inside the other.one millwheel was much bigger than the other and was hollowed out and the smaller was inside. they're both in line with each other and get hit with the wind at the same time. one moves clockwise and the other counter. the inside one does what turbines do anyway. the outside one moves what would be the stator(so again its a second rotor). relative rpm between the two increases for the same wind. aside from needing a stronger material, would it harness more power?
  7. kf

    wind turbines

    any reason why it would not be possible to have two sets of blades on a turbine. one would be in front and would turn the first rotor clockwise and another would be behind and turn a second rotor counterclockwise.(no stator)so the relative movement between the two rotors is much greater than the movement for one rotor and stator in for the same wind blowing at it. the first rotor could have 3 blades like a standard wind turbine. the second rotor obviously is blocked whenever it is directly behind the first so it would have maybe six? (or more) so that some blades are always exposed. so the rpm of the standard turbine would be x rpm relative the rest of the turbine. this design would have x rpm for the first and y rpm for the second.combining both would give a greater rpm for the same wind. is this idea just utter bananas? is the force of the wind behind a turbine very little compared to the front force in front due to turbulence being affected by the turbine to not make it feasible?
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