help! electricity generated from motor

Discussion in 'The Projects Forum' started by kirayamato_143, Aug 1, 2011.

  1. kirayamato_143

    Thread Starter Member

    Jan 23, 2011
    59
    0
    hi. Please help me with my project i'm planning to produce electricity out of the electric motor of an electric fan.. as electricity power the electric fan it should produce electricity that will light a bulb.. this is my energy saving project please help me. is this possible?..
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,768
    928
    If it is an AC induction motor, then your plan will not work. 99% of amateur type generator projects are made from DC motors.

    AC induction motors CAN generate electricity, but the motor must be supplied with electricity and be driven FASTER than it runs as a motor, to begin to generate electricity. Several large scale wind turbine schemes use these type of motors because they can generate electricity that is easily sent back to the 'grid' due to the fact they are already 'in phase' with the grid power because of how they operate.
     
  3. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Perhaps obtaining a DC motor and lighting up some LED's. How would you be spinning the fan/motor. Were you hoping to let the wind turn the fan and generate the energy?
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,089
    3,027
    As noted, you need a DC motor, not one from a typical household fan, which is AC.

    Be realistic about your load. A bicycle generator can make ~6W and places a noticeable load on the rider. If the rider is stationary and just making electricity, 100W is doable but not sustainable over long periods except for conditioned riders.

    If you want wind to do the work, find a table of swept blade area (or diameter) needed to get the power you want from a windmill at a wind speed of, say, 10 mph. You'll be surprised how big it'll need to be.

    That's why everybody lights up LEDs for demonstrations - they don't need much power.
     
  5. robporter59

    New Member

    Aug 31, 2011
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    0
    Hi, I also wanted to do this - for a teaching demo. I concluded the most practical way was to rig up a motor vehicle alternator, and then to use an inverter (the sort that plugs into the 12V socket of your car) to obtain AC 230V. This type of set up should handle a hundred watts or more and be roughly matched to a fit bike rider. If the bike had suitable gears most people could 'have a go' at their own fitness level.

    I have not built this yet so I'd be interested to know if there's agreement, and whether anybody has had success?

    My ultimate goal is to get the class to heat their own cups of coffee to show them just how hard it is, and how much energy they are using in the home etc!

    Cheers
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    An automotive alternator actually creates/generates AC. The AC is then rectified and turned to DC. By removing the rectifiers from the alternator you can eliminate the need for the inverter. The only problem is that an alternator puts out three phase AC. http://www.alternatorparts.com/understanding_alternators.htm
     
  7. wayneh

    Expert

    Sep 9, 2010
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    Actually there are two additional problems. An automotive alternator doesn't use permanent magnets and relies on a DC power supply to the field windings to create the magnets. The good part of this is that the load on the alternator can be controlled by changing the field current.

    The second problem is rpm: Automotive alternators expect to run in the thousands or rpm, faster than the engine running them. That's tough to achieve with bicycle-type mechanics, although certainly something can be produced at much lower rpm.

    Oops, one more problem; the inverter expects to see a steady 12-16V or so. Without a regulator, the alternator will be putting out a wide range of voltage proportional to rpm and field strength. This would work for a straight-to-heater (or light bulb) arrangement as suggested, skipping the built-in diodes and inverter, both of which waste power.
     
  8. PowerofRa

    New Member

    Jul 29, 2011
    4
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    I just though that this may be appropriate for what the OP is trying to learn about.
    http://www.allaboutcircuits.com/vol_2/chpt_13/8.html

    Down near the bottom of the page where it is talking about doublly-fed induction motors can be used as a generator. But thats a very specific setup, not quite what you've got in that fan motor.
     
    Last edited: Aug 31, 2011
  9. nucleargungus

    Member

    Apr 6, 2009
    23
    1
    Just wanted to be a bearer of bad news and point out one other problem if its like a box fan or something similar they have shaded pole motors which are super inefficient and provide enough torque to turn diddly squat

    Robert
     
  10. kirayamato_143

    Thread Starter Member

    Jan 23, 2011
    59
    0
    your explanations spins my head...never thought its that complicated but ill be trying a to experiment in two 5v dc motor the one spins the pan and the other is connected to the same motor but will be producing voltage connected in voltage amplifier,,i dont know if that makes sense i'm such a newbie guys sorry,,give me simple resource books if you think i need it..lol
     
  11. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    If what your trying to do is "perpetual motion" it doesn't work. One motor turning a generator will NOT run the motor. There are to many losses both electrically and frictionally to overcome.
     
  12. wayneh

    Expert

    Sep 9, 2010
    12,089
    3,027
    It doesn't. :confused:

    Can you draw a diagram of what you want to do? It sounds like you want to use one motor to turn the other. Is this just to demonstrate that the second motor can make electricity when turned? Anyway it's good that you're now working with DC motors.
     
  13. kirayamato_143

    Thread Starter Member

    Jan 23, 2011
    59
    0
    yes thats what i have in mind to turn another motor using another one,, but shorbus is right,,its my idea that i'm thinking to have no sense.tnx
     
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