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Trying to build a relatively simple Electric Generator.

  1. May 15, 2013 #1
    Hey, I'm new to this forum and registered specifically to ask people who know what they're talking about how I can make a generator for a wind turbine I'm trying to make. I'm in my first semester of college, and only have a high school education when it comes to physics, so obviously I've got very little knowledge. I understand that you need magnets to create a current within coils or wire, but I don't quite understand how they need to be set up, or how to calculate the expected output for a generator based on it's size and contents. I could REALLY use the help. I'm trying to build a small wind turbine to counter a bit of my electricity use.

    Honestly, I have a few ideas on how I might make it based on things I've seen, just can't trust myself to make one that would make enough electricity to be worth the cost.
     
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  3. May 15, 2013 #2
    Making an effective ( reliable, operational and efficient) generator is more difficult than it seems. If you only need to show actual electrical generation from wind energy - you may still want to start with a kit, or you will spend a lot of time selecting and acquiring parts.
    To build one effective enough to generate electricity to offset your usage, is much more involved - and almost a different project then learning about the generator itself.
     
  4. May 16, 2013 #3

    jim hardy

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    It'd be hard to beat a surplus car alternator driven by bicycle chain....

    Power company actually has the advantage because they buy fuel by the trainload.

    Unless you're way up north I believe you'd get better payback with a solar water heater.
    U of Fla did a study in 70's and concluded the old fashioned copper flat plate in a redwood box is mighty hard to beat. It has no moving parts so is virtually zero maintenance
     
  5. May 18, 2013 #4

    sophiecentaur

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    Auto Electrics manufacturers know what they're doing and have spent nearly a hundred years getting it right. Car breakers always have these things for a reasonable price. However, a car alternator is for generating hundreds of Watts and needs to rotate at at least 2kRPM. (Any up-gearing will introduce inefficiency.) There are some very good bicycle alternators available (not the ones with a pinion rubbing against the tyre, but the 'hub' type) that will provide just a few Watts and would not need a lethal scale of turbine size. I have a version of this on my boat. It is very low power, producing about 2A at 14V in a good breeze. Ridiculously expensive bit of kit but it does the job of keeping the battery topped up and it's been going for more than five years.
     
  6. May 18, 2013 #5

    jim hardy

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    Automobiles also have small permanent magnet(PM) motors that might be adapted.

    Since this is a learning venture, you might benefit by taking apart a few and reading about them.

    Heater blowers, electric windows, electric seats, radiator fans are all DC machines in the "several" ampere range which is, as Sophie points out, more suitable than the 100 amp alternator. And the PM versions don't need excitation.

    Spend a day at a junkyard . One learns a LOT by taking apart things that are already designed.
    I can vouch for Ford windshield wiper motors being pretty robust. The older ones are three-brush, quite interesting devices..

    This youtube shows the principle. Take apart some real motors to see how it's done for real.


     
    Last edited by a moderator: Sep 25, 2014
  7. May 28, 2013 #6
    I was just reminded of used treadmill motors - pretty widely available on e-bay. Typically DC output.
     
  8. May 28, 2013 #7

    sophiecentaur

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    You need to avoid anything with integral gearing. This may introduce inefficiency. In the case of a high ratio of 'gearing down' it can be catastrophic (as with a work drive, for instance).
     
  9. May 28, 2013 #8
    The treadmill motors are used frequently for DIY windmills. They are not typically internally geared, belt drive gives most of the ratio but not much of conversion is needed - the shaft speed is pretty close to the necessary tread speed.
     
  10. May 29, 2013 #9

    sophiecentaur

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    Oh, I didn't realise that. I was assuming there'd be some gearing involved. Still, it was worth making the point about steering clear of motors with non-direct drive.
     
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