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Electrical generator- governing laws for RPM to voltage output

  1. Jun 21, 2008 #1
    Hello all,

    Is there anyone out there who can help me out?

    I have developed a drive system for a generator, but... the big but.... in need to know how to build the appropriate stator for it.

    Assume this is of the windmill electrical generating variety, where magnetic coils produce AC current using reverse polarity magnetism.

    But.... another big but... the RPM's are around 5000, consistent.

    So what are the laws governing the wire gauge, the turns, the number of coils, number of magnets, space between coils, space between magnet, space between magnets and coils.... and all designed for a ridiculously high RPM.

    For those of you with the appropriate engineering degrees, and can give me all the answers I need, there will be a monetary remuneration for credible advice. You can e-mail me through this site.
  2. jcsd
  3. Jun 21, 2008 #2
  4. Jun 21, 2008 #3


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    Something that might come close to what you described, they also have 3hp cont. duty PM DC motors (that I think are very good, if their not sold out) right at $60.00 US


    The mount bracket can be removed by unscrewing three bolts that secure it to the housing.
    Last edited: Jun 21, 2008
  5. Jun 22, 2008 #4
    Thanks guy

    Most of what i found through your recommended sites I have already researched quite thoroughly. Especially the windmill generators.

    My biggest obstacle seems to come with the high RPM. Windmill generators run at low RPM's and therefore much of what they suggest doesn't take into consideration the wire gauge and turns required to handle both the efficiency and energy loss.

    So again, I'm looking for those specifications that will work at 5000 rpm's
  6. Jun 22, 2008 #5


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    I'm a little confused, if your windmill is turning at 50 RPMs and you have a 100:1 stepup ratio, the motor would be turning at 5,000 RPMs, at that speed the voltage would be around 110v, and your best amperage output would be around 2a or 3a Amps. The output of amps will be related to your blades surface area.

    The motor specs again were,

    6750 rpm
    18.5 amps

    If given this much power the output is 2.5 horsepower, the duty cycle however is NOT 100%.

    Turning it as a generator @ 6750 rpm will give a voltage output of 130AC and 0 up to 18.5 Amps current delivered. The duty cycle of this motor will be determined by the total wattage drawn from it.

    If I'm wrong someone will step up with a correction:wink:
  7. Jun 22, 2008 #6
    Thanks again

    I'll look into this motor, which I believe would probably answer a lot of my questions, but if it has brushes, which I assume it has, then it is not what I'm looking as. I'm looking at something with almost negligible resistance.

    Most motors, by the nature of their design with no current running through them have a lot of resistance due to the magnets.

    That's why i want to build my own stator, again like that of windmill generators, where the magnets are completely independent of the coils and no wires touching, except for those to the coils of course.

    But I understand where you're going with this. You're saying that if I take this motor apart, it would probably give me an indication of what a high RPM requires. It may be worth buying just for the investigative illumination.

    Thanks RonL
  8. Jun 22, 2008 #7


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    Sorry! I did kinda gloss over what you were saying.
    I have about a dozen of these motors that I have used in various way, and almost all were fairly low power applications and none that were precise enough to worry about PM, and brush resistance.

    I like them (especially the price), but have not put any to a maxium test.
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