producing power with 3 phase motor

Discussion in 'The Projects Forum' started by mack2k, Mar 26, 2009.

  1. mack2k

    Thread Starter New Member

    Mar 26, 2009
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    I need to know what size or HP motor 3phase I would need to operate as a generator and operating it off a smaller 3phase motor running off single phase to produce enough KW to power my home..

    I am talking about making a rotovetor with the smaller motor running on single phase..I think that to be safe I would need to be able to produce 20-22 KW of power.. I think a 30HP motor would produce 22,3721 KW..

    I appreciate any and all help on this and has anyone of you ever tested this setup and is it possible to cut the power bill in at least half..
    I just think there is a way to give us some freedom for the power company
    thanks ..mack
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    It won't work.

    You'll wind up using more power, because of the inefficiencies.

    If you want to save money on power, put in more efficient lighting, set your thermostat to a more economical setting, and use the microwave more than the stove/oven.

    And install solar panels, add insulation, yadda yadda yadda.
     
  3. mack2k

    Thread Starter New Member

    Mar 26, 2009
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    thanks for the reply...I understand what you are saying.
    I would like to know if there are some elec engineers out there that have seen this tried and tested...would it be possibe for the rpms to fluculate with the amount of load..thanks mack
     
  4. AlexR

    Well-Known Member

    Jan 16, 2008
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    I am not an electrical engineer and I have not tried or tested this but then neither has anyone else on the world because what you are trying to do can never work. In effect what you are proposing is a perpetual motion machine and no-one yet has succeeded in building on of those.

    Getting the RPM to fluctuate with load would be very easy, in fact I am sure that it will fluctuate, the difficult part is keeping the RPM constant. RPM determines your supply frequency and power companies go to a lot of trouble to keep the frequency constant. Most electrical appliances are designed with the assumption that they will be fed with a set frequency. It you feed them with a frequency they are not designed to work with you will probably damage them.
     
  5. recca02

    Senior Member

    Apr 2, 2007
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  6. SgtWookie

    Expert

    Jul 17, 2007
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    The only reason to do what you are proposing is if you only have single-phase power available, but you have industrial tools (like milling machines, etc) that require three-phase power to be run on an occasional basis. There are such motor/generator pairs available, but the trend is towards all electronic inverters.

    Neither method achieves 100% efficiency, due to inherent losses that simply can't be eliminated.

    What your initial post suggests is that efficiency exceeding 100% is possible, which is not.

    And for your 2nd question; for an electromechanical generator, yes - if load varies, the generator RPMs will fall, but the controls for the system will attempt to stabilize the frequency as close as possible to what it's designed for.

    The fully electronic inverters' frequency output won't be affected by loads.
     
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