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Question about Toroid wiring

Discussion in 'Power Supplies' started by dvc2013, Jul 9, 2013.

  1. dvc2013

    dvc2013 New Elf

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    Hi from up here in the U.S. I'm hoping someone can give me a little help with wiring of a Toroid transformer. I have several display elements that are using 24 volt sections of 10 or 11 incan-minis. Instead of using 6 or 8 small 24 volt transformers I thought it would be better to use a toroid since Iv'e already had it for quite a while but haven't used it yet.

    So here is my question. I am confused about the primary wiring. It has 2 separate 117 volt primary coils. If I connect either one of the primaries, I get about 25.5 volts on both of the secondaries. If I connect both primaries to my 120 volt supply it blows the fuse on the mains supply.
    Why do I have dual primaries ??? Can I connect them in series and supply the primaries with a 220-240 volt supply ??? Or am I over thinking everything and I just need to connect one of the primary coils ??? I know toroids are widely used in Australia so I thought maybe somebody down there could give me an explanation or some advice.
    I will try and attach a photo of the toroid I'm trying to use,

    Thanks for any help you can give me before I burn my house down.
     
  2. David_AVD

    David_AVD Bite my shiny metal ass!

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    You should make sure the primary windings are in phase.

    For 120V, use Yellow and Red as one connection and Orange and Brown as the other.

    For 240V, connect Orange and Red together (and nowhere else) and use the Yellow and Brown as your 240V connections.
    If you only connect one primary winding (for 120V), the output current will be reduced by half and the unconnected primary will have 120V sitting on it!
     
  3. OP
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    dvc2013

    dvc2013 New Elf

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    Hi David and thanks for the reply.

    OK, so that resolves my issue with the primary side. When both primaries are wired as you suggested, it no longer blows the fuse connected to 120 volt supply. However I get 221 volts on each of the secondaries.
    Do I need to connect them together in phase as well ??? If so I am assuming (Iknow bad idea) that they should be connected in parallel somehow in order to get the full current output.
    Thanks you have been a big help already. I may end up powering on 220 volt supply which is not a problem if I need to. Besides, t's more efficient that way
     
  4. David_AVD

    David_AVD Bite my shiny metal ass!

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    I sounds like you may have gotten the primary and secondary winding mixed up. (same colours are used on some Pri and some Sec wires by the look of it)

    The primary wires should be fairly thin and the secondary ones quite stiff.
     
  5. OP
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    dvc2013

    dvc2013 New Elf

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    I don't think I have them mixed up. It's pretty easy to tell the difference. The secondary is the larger wires. The primary ones are fairly small.

    So, like I said I understand the primary side now. But I have some confusion with the secondary.

    Maybe wiring the primaries in series and using a 220 volt supply is the best. Besides, it will give the maximum output current available. It should give me 690VA instead of only 345VA.
    Thanks for your patience with me will I figure how to wire my first toroid.
    Thanks again for your help and suggestions.
     
  6. David_AVD

    David_AVD Bite my shiny metal ass!

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    When mounting a toroidal transformer, use the correct hardware (dish and insulators) and don't let the top of the bolt (where the nut is) touch anything. The bolt is effectively a half-turn and connecting both ends can lead to heating and sparks.
     
  7. OP
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    dvc2013

    dvc2013 New Elf

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    Hi David,


    Thanks for the info on the mounting.


    220 volts it is. That seems to make the most sense and that's how I have it wired for testing and all is well.


    Thanks Again for all of your advice.
     

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