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Using HDD motor as generator

Discussion in 'Renewable Energy' started by mygatt3, Feb 28, 2010.

  1. mygatt3

    mygatt3 New Member

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    I am making prototype windmill and am using a Hard disk drive motor as my generator. (or intend to) I believe this is a three phase motor and i would like to know what i would need to make it generate the correct energy to charge two AA batteries.
    (What are the main things i may need and need to do?)

    Thank you for any help!
     
  2. dknguyen

    dknguyen Well-Known Member

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    You would first need a 3-phase diode rectifier to convert the 3-phase AC output of the motor into a unipolar voltage among other things. From there you need to smooth the voltage as it has lots of ripple to get something like a DC voltage which would then need to be regulated somehow.
     
  3. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    You may run into the simple problem that as motors they spin at 5000 - 7200 RPM off of a 12 volt source.

    To generate 12 volts may take 8000 - 10000 RPM so even at 4 volts the speeds involved will still likely be in the 2000+ RPM range at no load. Thats rather fast for a small wind driven propeller unless you have 20+ MPH winds to drive it or very efficient prop design with excellent aerodynamics for maximum RPM outputs.
     
  4. dave

    Dave New Member

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  5. Vizier87

    Vizier87 Active Member

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    why don't you use a reversed dc motor? they're quite okay, mine (a small one) generated around 5-10V at 3000 rpm.
     
  6. mygatt3

    mygatt3 New Member

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    I dont think i will need 12 volts to charge 2 AA batteries... Correct? Is there any clarification on how to wire it correctly? I have everything pretty much built except for the electronics. The blade spins very quickly and seems to be very efficient.
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Just six diodes to make a three phase rectifier and bung it directly on the batteries - and monitor how it charges. If it does overcharge, then use a comparator to dump the excess energy to a dummy load (shunt regulator).
     
  8. mygatt3

    mygatt3 New Member

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    Can you tell me what kind of diodes to use? and what do you mean by bung?
    sorry for such questions.... i just want to get the right stuff and am new to this stuff

    thank you
     
  9. Hero999

    Hero999 Banned

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    It's slang for put, throw, push etc.

    In this case he mean connect the three phase bridge rectifier to the motor and connect it directly to the batteries, positive to positive and negative to negative.
     
  10. mygatt3

    mygatt3 New Member

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    [​IMG]

    [​IMG]

    [​IMG]

    here are some pictures of my windmill so far just need to get the wiring done...
     
  11. Vizier87

    Vizier87 Active Member

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    how fast does it turn with a table fan blowing on it?
     
  12. mygatt3

    mygatt3 New Member

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    it spins quite fast, fast enough where i cannot see each single blade spinning
     
  13. Vizier87

    Vizier87 Active Member

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    at full load? try and short the terminals. That's near the real speed you'll attain when you want to recharge the batteries.
    If you're thinking of building your own rectifiers, use schottky diodes. They have very low forward voltages, so more voltage output for your generator.
     
  14. Grossel

    Grossel Member

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    HDD motors NOT same as stepper motors

    This is wrong. HDD motors doesn't have any static magnets (like regular step motors) as they are type reluctance motors. That means they won't generate any effect out, unless they already is connected to a 3 phase voltage source.

    Diode bridge cannot be used for DC power out, but three half-bridges generating somelike threephase should make it suitable as DC generator.
     
  15. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I thought they were DC brushless motors?, with static coils and a permanent magnet rotor - no brushes, so how could they feed power to coils in the rotor?.
     
  16. mygatt3

    mygatt3 New Member

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    so what would i need to make this a DC generator?
     
  17. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    What I see in the picture is that it has four leads so that would make it most likely a two phase motor. You will need two bridge rectifiers to get the highest level DC output off of it. It's most likely a small permanent magnet two phase motor so it will work as a generator to some degree but you may find out that you need very high RPM's to get anything useful from it.

    As far as "it looks like its spinning fast" doesn't mean a thing in relative terms of speed. A few hundred RPM looks fast but its not any where close to what it may need to be able to even generate the four or so volts at tens of Ma's that is needed to charge a set of batteries.
     
  18. smanches

    smanches New Member

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    Which hard drives are you looking at? The typical modern HDD is a 3 pole brushless DC motor.

    I would agree that they are not the greatest for generating electricity. Too high RPMs are needed to get anything useful.
     
  19. mygatt3

    mygatt3 New Member

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    I just liked the motor because of its size and shape lol If it isnt going to work well what would be the most efficient motor to use? For my class we are testing them with fans... which isnt realistic but... (we will have a fan pointed at our prototypes for about 5 minutes and whichever can power a led the longest from a battery after that five minutes of charging wins lol)

    other constraints: must be no larger that 2 feet tall and 4 cubic feet

    Any suggestions on what would be the best?


    thanks
     
  20. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Why not test what you have - stick a multimeter on the poutput (on AC volts) and see what you get out when you spin the motor.
     
  21. mygatt3

    mygatt3 New Member

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    I think im going to hook it up to two bridge rectifiers tonight and see what i get out of it tonight with the fan and go from there
     

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