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Homemade Toroidal Transformer

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by abbarue, Jun 22, 2008.

  1. abbarue

    abbarue New Member

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    I was considering building my own toroidal transformers using 18awg soft steel wire for the core.
    I want to wrap the wire into a coil of the width and thickness I need and
    then wrap the copper wire around that to produce the transformer.
    I need a fairly large toroid of a certain size and dimension.
    Any advise on how to go about doing this.
    I already have the soft steel wire, I tried running a strong magnet over it
    and proved it doesn't stay magnetized, so it should work for the core.
    I know this is a pretty crude way to make a transformer but it's the cheapest
    way to get the size I need.
    I'm not sure of the exact dimensions I need yet thus the reason for
    making my own cores; so I can test various sizes without spending a fortune.

    So any advice would be greatly appreciated.
     
    Last edited: Jun 22, 2008
  2. mvs sarma

    mvs sarma Well-Known Member

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    the wire pieces or the turns what would make a circular toroid need to be insulated from each other. otherwise, the so called IRON LOSS would be high.
    over the wire core formed like what you propose, you need to wind copper wire with due care taken for insulation. you need to know the permeability of the core formed by you. this helps in computing the turns needed.

    In the olden days, transformers were made using this technique, for voice frequencies, as designed by British Post office (Now BT)3000 type phone instruments.
    BTW, you can get lot of surplus current transformer type cores (toroid type), you may try out , with proper calculations using the type core-- with due care ensuring that the core doesn't saturate .
     
    Last edited: Jun 22, 2008
  3. abbarue

    abbarue New Member

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    I got the idea from an old Tesla patent I seen.
    It appears this was how he made his first transformer cores.
    I don't recall the patent I was viewing.
     
  4. dave

    Dave New Member

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  5. Ubergeek63

    Ubergeek63 Well-Known Member

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    sure, back when there was nothing worth using.

    start by telling us you application. at 50Hz it would be very lossy but functional, at 50KHz you would not get anywhere.

    if you are trying to make a switching transformer, start with a $5 toroid inductor. with luck you will have enough space to hand wind the other winding.
     
  6. Mikebits

    Mikebits Well-Known Member

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  7. crutschow

    crutschow Well-Known Member Most Helpful Member

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    To insulate the iron wire, you can dip it in schellac prior to winding.
     
  8. Sceadwian

    Sceadwian Banned

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    Make some kind of mold in the shape of the toroid maybe with wood and line it with paper or just spray it with a couple thick coats of clear coat to act as a 'mold release' Grind up a bunch of iron filings as fine as you can, maybe find an old blender and start grinding up the 18 AWG you have. Use some over the counter epoxy and use just enough epoxy to give you a very thick paste. Press that into your form, let it cure and when you're done it'll probably look ugly as hell, but should work fine. Sand it up if you want a nice appearance.
     
  9. abbarue

    abbarue New Member

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    Another question about toroidal transformers.
    If I took a toroidal core and cut it in half to get 2 air gaps 180 deg. apart,
    how would this effect its operation?
    I read air gaps can help the transformer work better for some things.
    The reason I ask is that it would be much easier to wind a toroid if it was cut in half.
    Just wind as many turns as one wants around each half and then place
    the toroid together with a slight air gap in it.
    Much easier to wind a coil straight from a large spool instead of having to use a bobbin.
    It's hard to estimate just how much wire to wrap around the bobbin.

    What do others think of this idea?
     
    Last edited: Aug 14, 2008
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Certainly I think "why would you want to do any such thing?", winding a toroidal transformer sounds a silly idea.

    What exactly are you trying to do?.

    If you cut a toroid in half it's not a toroid any more, it's a C core transformer.
     
  11. rjvh

    rjvh New Member

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    Sound a bit contradicting to me but why you don't tell us what you want to achieve

    maybe there are members here that can help you to find what you need for a cheap price or a better/cheaper solution for wat you want to make

    I don't think its some kind of device that you build to supply to a highly secrete nasa space program

    Robert-Jan
     
  12. Hero999

    Hero999 Banned

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    I hope this isn't a mains transformer, if so it isn't just a silly idea, it's a totally stupid idea.
     
  13. Sceadwian

    Sceadwian Banned

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    I think the point is the ease of winding. Toroids have less of an external magnetic field than many other core types. He just wants to know what effect cutting the toroid in half for winding and then gluing or binding it together will have.
     
  14. abbarue

    abbarue New Member

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    The reason for asking this question here is because of the following statement I read on another forum.

    "If a unidirectional pulse current is passed through the centre the toroid becomes magnetized and the field remains in the core unless a demagnetizing field is applied to reset it or an air-gap is introduced. This is due to the finite area of the BH loop."

    If that statement is correct then it would be very beneficial to have an
    air gap in the toroid.
    And I saw a second benefit to the air gap making it easier to wind.
     

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