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transformer core

Discussion in 'General Electronics' started by Kevin Weddle, Feb 25, 2004.

  1. Kevin Weddle

    Kevin Weddle Guest

    What is something that I can use for a transformer core? A piece of
    steel that has a large area is what I think I need. Do I have to find
    a steel shop? The example core that I have seen has a large area as
    opposed to just length.
  2. Robert Baer

    Robert Baer Guest

    It is not "ordinary" steel; it is a special alloy.
    One can get surplus transformers with sufficent window area for
    proposed windings, and use the laminations from two or three same-sized
    transformers to build a larger power transformer than what is otherwise
    And do you know how much power the proposed transformer must handle,
    so that youcan calculate the required cross-sectional area?
    And then, calculate the number of turns per volt?
  3. Kevin Weddle

    Kevin Weddle Guest

    I understand that the winding itself should be able to handle the
    current. But if a coils core is too small, the current will destroy
    the winding?
  4. Robert Baer

    Robert Baer Guest

    Getting the proper wire size is simple and not related to power level.
    If one draws an excessive current, then one or more windings get hot
    and can cause a small fire.
    If the current is really large, hopefully the mains fuse or circuit
    breaker will act as protection.
    Then again, one time someone plugged a "short circuit" into a 110V
    outlet, and a flame shot out 2-3 feet for well over 15 minutes, and the
    15 amp circuit breaker did not even think of tripping.
    That half of the outlet was turned very black, and all of the copper
    there was vaporized (top half almost completely intact).
    I am guessing the arc current was a mere 10-12 amps...
  5. Bill Vajk

    Bill Vajk Guest

    Failure to trip is common in some brands. Federal Pacific bribed their
    UL approval for decades (well documented in the press at the time it
    was discovered.) I've personally experienced failure to trip in FP
    breakers at sometimes 6 to 7 times the rated current.

    In addition, as inexepnsive as the typical circuit breaker is, they're
    just not all that reliable. If you absolutely positively *must* have
    reliability, stick to fuses.
  6. Robert Baer

    Robert Baer Guest

    I agree on the reliability statement.
  7. Bill Vajk

    Bill Vajk Guest

    Here's some more info:

    Also you can google "federal pacific" UL

    (don't forget the double quotes) and get some 227 hits.

    My 6 to 7X current was on a 20 amp single pole FP breaker.
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