Re-wiring a Transformer

Discussion in 'General Electronics Chat' started by adam555, Dec 19, 2014.

  1. adam555

    Thread Starter Active Member

    Aug 17, 2013
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    Hi,

    I dismantled a 220V to 12V transformer thinking it wasn't working. I put it back together, and after checking it was fine, I though about the possibility of re-wiring it to make it 6V-0-6V instead of 12V; as I have more use for this type of configuration.

    I was planning on leaving the primary exactly as it is, un-wire the secondary, cut it in half -connecting one side of each half-, and then re-wire each half in opposite directions; leaving the union as the central tap and each side as separate 6V taps.

    Would this work?
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    no, just find the ce3nter, bring it out. winding in the oposite direction is wrong.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    what is the cost of a 6-0-6 transformer in your country, is it worth the effort of un/ rewinding it ?
     
  4. adam555

    Thread Starter Active Member

    Aug 17, 2013
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    Last time I bought one, the cheapest option was ordering it from the UK on ebay; it was far more expensive than spending 10 minutes recycling this one.

    I thought about that but, won't I need to unwire the secondary to find the center; or is there another way?
     
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the thing is that if you wire the two halvs oposite directions, it will not work. regardless of how you rewind the transformer, or add the tap.
     
  6. adam555

    Thread Starter Active Member

    Aug 17, 2013
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    Well, what I meant by re-wiring them in opposite directions will be practically the same as finding the center and bringing it out, with both sides re-wired in the same way as they are now; only that a cut and connection will be in the middle. One half wired clockwise, and the other half counterclockwise; with the middle connection in the center, and each side coming out on each side.
     
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    best way is to use a voltmeter and unwind some turns and measure the output, when you get to 6v, tap it and rewind it in the same direction.
     
  8. adam555

    Thread Starter Active Member

    Aug 17, 2013
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    This is what I meant by opposite directions:

    WP_20141219_002.jpg

    Isn't the wire coated? I mean, wouldn't I need to remove the coating to make each measurement?
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I have rewound my share of transformers in my frugal past, the easiest being toroidal of course.
    If using the two windings in a balanced form, you should really wire them bifilar or both together, whether using for C.T. supply or in parallel, you would need about 2 turns/volt.
    Max.
     
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  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You can wind it in opposite directions as long as you bring all four ends out for maximum utility and phasing
    Max.
     
  11. adam555

    Thread Starter Active Member

    Aug 17, 2013
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    Thanks Max,

    Bifilar also seems much easier than winding each separately in opposite directions.

    I would have never though of doing it that way; it kind of sounds counterintuitive. But after a google search I found it's quite common.
     
  12. adam555

    Thread Starter Active Member

    Aug 17, 2013
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    One question -I'm also trying to learn about transformers with this exercise-: if I do it bifilar, and I measure the voltage on each extreme, would I still get 12V; as I would in opposite directions?
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You will end up with two 6v windings which can be used either in series or parallel, it is important to phase them properly for parallel use, otherwise you fry the transformer, but has to be done for both instances.
    The object of bifilar is to retain voltage balance.
    Max.
     
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