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AC generator design problems

Discussion in 'General Electronics Discussion' started by Jim M, Feb 11, 2013.

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  1. Jim M

    Jim M

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    0
    Feb 11, 2013
    I am building a AC generator - 12 magnets (2" dia - 1" thick) and 9 coils - face of the core is also 2" dia. the core is mild steel. when the mags pass over the steel cores eith NO COPPER WIRE wound on it the steel gets very, very HOT (changes color). Is this normal ? is there a way to stop this heat build-up. would facing all the mags with North or south all on one side of the rotor help? are the mags TOO Close to each other - should there be more space between them.since the mags are 2" dia should there be a 2" space between them . we are only testing with ONE core at this time and this one gets very hot.
    can anyone with more knowledge help?

    thanks,
    Jim
     
  2. john monks

    john monks

    693
    2
    Mar 9, 2012
    I understand that you are passing magnets in a circular fashion around the surface of a steel plate and the plate is getting very hot. If this is so then you are generating "eddie" currents in the steal itself. To stop this current you need to laminate the steel.
    The principal is this: When you pass electrons through a magnetic field the electrons will have a force placed on them perpendicular to the direction of travel and perpendicular to the magnetic lines of force. And in a conductor the electrons will travel and this is what is happening in the steel plate. So you need a laminated steel plate or a powdered iron plate and the problem will be greatly reduced.
     
  3. Jim M

    Jim M

    3
    0
    Feb 11, 2013
    thanks for the reply. what type of material should i use ? will laquer work on the ends of the steel poles? should i spray this on.

    thanks
     
  4. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    The core needs to be laminated as said. Look at an old, broken heavy wall wart and look at the transformer laminations.
    A good alternator design is used for car generators. Get a faulty one from a scrap yard and see how it is constructed and how the poles are laminated.

    You might need a big hammer!

    Transformers are sometimes laquered, this does nothing for the action of the transformer but it can stop lamination buzz.
     
  5. Jim M

    Jim M

    3
    0
    Feb 11, 2013
    can i cut slots in the core face ( the part that faces the mags) to stop the eddy currents?
     
  6. john monks

    john monks

    693
    2
    Mar 9, 2012
    Keeping in mind that the electrons are forced perpendicular to the travel of the magnets you will need to use laminated steel as Duke37 describes. And the plane of each lamination need to be in the same direction of the travel of the magnets. For a steel plate this seems awkward. But the only thing that comes to mind right away seems to be something like a spiral strip. Otherwise you might consider using powdered iron for picking up the magnetic fields.
    The laminations should be insulated from each other using enamel varnish or some other insulating material such as is used in transformers or electric motors. Laminating the steel prevents current from traveling from one area of the steel to another.
    The steel is normally used to pass magnetic energy from the magnets to your coils that give you alternating current.
    Keep in mind that the traveling magnet should travel along the edge of each lamination.
     
  7. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    Find an old transformer with E and I laminations. Dismantle and rebuild with just the E laminations passed in from one side and try that. Pass the magnet over the cetre leg.The spool will give the output.
     
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