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Newbie needing motor advice

  1. May 9, 2009 #1
    Greetings everyone. My issue is this:

    I'm interested in finding a small electric generator that can power a standard vacuum cleaner motor for a project that I've had for quite some time but am only now getting around to trying to figure out.

    The idea seems simple enough, but I could use some advice on where to look for the electric generator I need.

    I do apologize if this is too vague, but I'm not fluent in technical jargon and mathematical language, (being a writer by design). Any advice you can give me will be greatly appreciated. Thank you.
     
  2. jcsd
  3. May 9, 2009 #2

    russ_watters

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  4. May 9, 2009 #3
    Thanks :)

    Continuous... i.e. DC current?
     
  5. May 9, 2009 #4
    Vacuum cleaner motors are generally AC-DC motors, and will draw less volt-amps running DC than running AC, but will also need less DC volts. The very high inductance of the motor requires about 7.2 amps at 120 volts (for our vacuum cleaner) = 860 VA, but less than half is real watts. Your generator has to be sized for V-A, not watts. So check out the VA rating of your motor.
     
  6. May 9, 2009 #5

    russ_watters

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    No, AC. Continuous is opposed to peak. When you turn on an electric motor, there is an inrush of current - a spike in power. A peak.
     
  7. May 9, 2009 #6

    russ_watters

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    My vacuum cleaner isn't a very expensive one and says it draws 12 amps.
    Just to clarify my post a little, I threw in some safety factor and oversimplified. Electroc motors aren't really rated in watts anyway, only amps, so if you call that 860 VA (1440 for mine) "watts", you're essentially adding about a 20% safety factor. I know it isn't technically correct, but it works here.

    You are correct that generators should be rated in VA, but I don't suspect a lot of residental ones are, since few home consumers would know the difference. Here's the spec sheet from a possible candidate from the site I linked earlier, and it doesn't mention VA (though it does say the amperage):
    http://www.electricgeneratorsdirect.com/manuals/5723_GP1800.pdf

    It lists a 7.5 A rating at 240 V for 1800 VA, but it only lists its rating in watts.... if you are doing a purely resistive load, the rating in watts is accurate, if you are doing a vacuum cleaner, the rating in watts isn't, but knowing this, my method dovetails with theirs pretty well to produce a useable answer.
     
    Last edited: May 9, 2009
  8. May 9, 2009 #7
    Vacuum cleaners are very efficient in making sound SPL (sound power level) decibels. Ours must over 100 dB. It scares our dog.
     
  9. May 9, 2009 #8

    RonL

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    If you have a vacuum motor, most likely Amtek supplied it.
    This link will give most data needed if you are working with the movement of air.

    http://www.ametekfsm.com/Product_CompareGraph.aspx?MT=1&PerformanceGraph=1 [Broken]
     
    Last edited by a moderator: May 4, 2017
  10. May 10, 2009 #9
    Well, i have a theory about consistently supplying electricity to a motor, but since I lack technical "know-how", the pulley and and belt system of a home vacuum seemed an easy place to start with attaching extra components to run with the belt system.

    EDIT: I really do wish I could use the jargon that would clarify what i'm trying to do, but I simply lack the language of electrical equations and such. I'm sorry for being a newb at this and I appreciate your patience.
     
  11. May 10, 2009 #10

    russ_watters

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    Please take safety precautions - we don't want your family to sue us when you electrocute yourself!
     
  12. May 10, 2009 #11

    RonL

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    The best thing to help clarify what you are trying to do is use simple words, the jargon and equations will come at a later time. Most household vacuum cleaners are designed to operate on house voltage of around 115 Volts, and 8-15 Amps, or 1,000-1500 Watts. This will set the maximum power you can use, and to try to exceed this will result in a burned out motor.

    When you sign on as a member of this forum, you have an opportunity to say a little about yourself, any information helps all who look at the "about me" to have some idea of the person and his or her background or abilities.

    The focus of the forum and almost everyone on it, is to be of some help in some way to as many people as ask for assistance.

    Now my guess is, your idea is not related to doing floors:smile:

    Ron
     
  13. May 10, 2009 #12
    My idea while having nothing to directly with cleaning floors is trying to use materials that are readily accessible; i.e. I'm broke and trying to accomplish something anyway lol. The simple way to describe what I'm trying to do is: to put a magneto or such electric generating motor on a system that has the same electrical requirements as said motor where the motor being powered by the "magneto" is turning the magneto to generate a continuous electrical supply to the motor, thereby creating a circuit where one motor feeds the other in a type of symbiotic relationship. But since I haven't the funds to go out and buy all the parts I need for this, I'm looking for advice on the best way to go about this.
     
  14. May 10, 2009 #13

    RonL

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    The best answer to your request is to give a simple illustration of a motor and generator combination, as you have described, first, no motor or generator is 100% efficient, but for illustration only, lets give them a 90% efficiency.
    If the motor draws power at a rate of 100%, it will deliver to the generator 90% of that power, then the generator loses it's 10% and the difference needs to be brought in from some other source.
    If the losses were to be recovered and your system became 100% efficient, the motor would turn the generator and the generator would supply the motor and the energy balance would be 0, no productive work could be drawn from it.

    Any thoughts are good if they produce a need to learn.

    Ron
     
  15. May 10, 2009 #14

    russ_watters

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    The law of conservation of energy is real, Astor, sorry - what youa re suggesting is impossible.
     
  16. May 11, 2009 #15
    I was watching the science channel and they had a robot with battery powered motors. Batteries need to be recharged, with the system I've mentioned, would not the power from the batteries contribute to the overall electrical output, thereby negating the [motor power needs]+[the generator power needs] = 0 problem mentioned above?
    If I change my idea a bit, to where the batteries power the motor, the motor in turn powers the electrical generator and the generator in its turn charges the batteries, would that possibly work?
    I'm not an old man, but I've been around long enough to learn that with technology, nothing is impossible for long.
     
  17. May 11, 2009 #16

    brewnog

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    Like a true crackpot spoken. I don't mean to offend, but please re-read the above posts, you can't run a motor off electricity made by a generator connected to itself; there are losses (inefficiencies) all over the system which you just can't ignore. Batteries just store energy; they'll run out soon enough, just as they would without the 'regeneration' idea.
     
  18. May 11, 2009 #17

    russ_watters

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    Ok.....
    You forgot a term in that equation: friction. For the robot, if it just walks around for a while, all of the mechanical energy created by the motors is lost as friction.
    I don't see how that is different from what you said before, but anyway, you already stated the equation correctly above, assuming no friction: the net output energy of such a system is zero. So in an ideal case, the net useful work output of such a system is zero - in a real one, the net useful work output is negative.
    Well this has nothing to do with technology, it is a fundamental principle of science. I don't know how long you've been around, but most people who have been around a while know that there really are limits to what is possible due to the laws of science.

    In any case, you can believe whatever you want, but we won't help you develop a pointless crackpot idea. Thread locked.
     
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