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Core Material for Induction Coils / Transformers

Discussion in 'Homebrew and Kit Projects' started by KK4NSF, Oct 13, 2020.

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  1. KK4NSF

    KK4NSF Ham Member QRZ Page

    In building HV transformers for demonstration pieces, I've noticed that the biggest problem is locating suitable core material, which needs to be a rod or bundle of small rods. The old books usually specify a bundle of "soft iron wire", which is virtually gone from the marketplace. Soft steel is not too hard to come by, but it has just a bit too much residual magnetism to really work well.

    There are some excellent transformer core materials out there, but the companies who sell it only want to deal with large maunufacturers and don't sell to individuals. SO.... where can one get good transformer materials? OR what are good alternative materials? I'm wondering if a large ferrite rod would work in this application?

    Any other ideas?
  2. W1VT

    W1VT Ham Member QRZ Page

    When I went to the University of Pennsylvania they had wonderful lab classes that allowed you to use unobtainium such as transformer core material and doped bars of semiconductor material.

    Zak W1VT
  3. KK4NSF

    KK4NSF Ham Member QRZ Page

    if only I were so lucky!

    I'm wondering about using a single bar of Vim Var from Ed Fagan....

    It looks promising, and I can get a piece that is .5" diameter. The question about that is whether or not a single bar will work, rather than a bundle of isolated small wires / rods?
  4. W1VT

    W1VT Ham Member QRZ Page

    The reason for small rods or laminations is eddy current losses. Calculate or estimate them and decide whether they are acceptable for your application.

    Alternately, one can obtain a material, measure it, and engineer your way around its issues.

    Zak W1VT
  5. SM0GLD

    SM0GLD Ham Member QRZ Page

    Use the iron core from a car ignition coil. At least the old one uses a bundle of iron wire.
  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Scavenge. Use the cores from old transformers. You can cut them to the dimensions you need. Disassembly will yield section forms of C,E, H, I; depending on the particular construction.
  7. KK4NSF

    KK4NSF Ham Member QRZ Page

    scavenging from old transformers / coils is a good idea, but I'd like this project to be as good-looking as possible since it's going to be a demonstrator / display piece. New material would be preferred, if at all possible.
  8. W1VT

    W1VT Ham Member QRZ Page

    Perhaps someone in marketing could get you some samples from manufacturing?
  9. SM0GLD

    SM0GLD Ham Member QRZ Page

    Is this a 60 Hz transformer?
  10. KK4NSF

    KK4NSF Ham Member QRZ Page

    it's a LF variable hertz device..... between ~50hz to maybe 200hz, depending on how the interrupter gear is set.

    DC input goes to Interrupter gear, then to the transformer..... at low frequency. Very similar to an induction coil.

    Last edited: Oct 13, 2020

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