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transformer core

Discussion in 'Electronic Design' started by Kevin Weddle, Feb 25, 2004.

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  1. Kevin Weddle

    Kevin Weddle Guest

    What can I use for a transformer core? I think I need a piece of steel
    with a large area. The example that I have seen has a large area, not
    just length. Do I have to find a steel shop for a core?
  2. What kind of transformer? A mains transformer? A pulse transformer?
    Audio Transformer? RF Transformer? Transformer core materials vary
    widely depending on the application.

    And what do you mean when you say "area"? Cross-Sectional area of the
    core? Of the winding?

    If you don't provide some details you won't get useful answers.
  3. On the tracks of the anchestors ? Building an educational
    transformer ?
    Actually steel is very wrong. Beside some special transformer
    alloys, pure iron without carbon or anything is the best.
    A bit of silicon improves it though. And having the
    crosssection made from sheets also improves.

  4. Mac

    Mac Guest

    Another important thing to consider is currents in the transformer. You
    don't want them. This is why transformer cores are typically made from
    many metal stampings which are glued together. The glue does not conduct
    electricity, so electricity can't flow in the core in the direction of the
    induced electric field gradient.

  5. Robert Baer

    Robert Baer Guest

    Sorry, it is *not* glue.
    Varnish used to be the potting material of choice, but there are some
    good plastics that can be used.
  6. Harlan

    Harlan Guest

    Mac is right about the core having to be laminated or some form of
    core designed to eliminate eddy currents.
    Kathy, This is a really neat project and there are so many things you
    can do to make this and make it work with minimal headaces. This core
    material will seem to be elusive with out a small study to what is
    happening. I will be starting a thread soon on designing a transformer
    from old parts here real soon. The eddy currents would cause the core
    to get hot, and heat destroys the magnetism and that stops the current
    from transfering and the primary current then goes real high and then
    you have smoke everywhere. Eddy is a bad thing!
    You can actually get good core material by scrapping out an old
    transformer, and is a great way to recycle materials that get thrown
    away needlessly. The Iron in a transformer is the most expensive part,
    and salvaging one for a project is great. I would recommend reading a
    little on Volt Amp characteristics to make sure you get a core of the
    right size for you project. Depending on the load current, (total VA)
    something like an old ballast core may work fine too. And here all you
    have to do is cut the old wiring away, salvage the laminations and
    clean things up, make a new bobbin and wind the transformer to your
    own design. There is a LOT of information on the net to help with as
    Just a thought here.
    Good luck
  7. Kevin Weddle

    Kevin Weddle Guest

    Okay. This is a power autotransformer. The core that I need then would
    be just iron and not steel. I'm not going to glue or strip apart a
    transformer. I can't measure the inductance, but I can calculate it.
    This means that I'm sure that I will have inductance. The question is,
    how good will it be.
  8. Boris Mohar

    Boris Mohar Guest

    It will be crap. Look up eddy currents to start with. Get a junk microwave
    oven and take out the transformer. The secondary is wound separately from
    the primary. Hack out the secondary and wind your own.
  9. I read in that Kevin Weddle
    I very much doubt it.
    Starting from where you are at present, good will not be the right word.
  10. You are very unlikely to have inductance since a lousy choice of core
    material will saturate.
    What you have instead is called an "induction heater".

    Using ~anything~ except a properly laminated and rated core material for
    the frequency and flux density of interest will almost certainly burn up
    at any reasonable power level.

    Many thanks,

    Don Lancaster
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    voice: (928)428-4073 email:

    Please visit my GURU's LAIR web site at
  11. Robert Baer

    Robert Baer Guest

    In short, you do not know what you are doing and have almost no clue.
  12. You can calculate the inductance? Pray show us how! I would be
    interested in the formulas (formulae?) you use.
  13. Mac

    Mac Guest

    Well, I was going to say "adhesive," but I was afraid that sounded too
    technical. If I had to guess what they actually use nowadays, I would
    guess that it was polyurethane, but I surely don't know.

  14. Mac

    Mac Guest

    You might be able to use a bunch of strands of insulated iron wire for
    your core. This would then be a toroidal core transformer. I've never done
    anything like this, but I am pretty sure that you can get insulated iron
    wire somewhere.

  15. Robert Baer

    Robert Baer Guest

    I would guess that as well, or a close "relative".
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