Rewinding transformer secondary - some strange questions

Discussion in 'General Electronics Chat' started by RogueRose, May 14, 2016.

  1. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4
    I have a 1500 watt Microwave oven transformer and removed the secondary. I've worked with these a good bit and made some various voltage outputs but this time I want to try something different.

    I'm using 10g solid strand with very thin teflon 600v insulation (makes wire .2mm thinner overall). I have 6 colors of wire. I plan on pairing all 6 and wrapping the coil with them. I've considered twisting them together but I think that would be a mistake and maybe take up more room, so "parallel"/straight wiring seems to be the best option.

    What I want to do is with each set of 6 do 2 turns and then cut leaving adequate room for stripping & connecting. I want to do this 3 times, so there will be 3 sets of wires that have been wrapped around the core twice.

    So if each color was connected in series I would have 6 turns for that wire.
    If I connected each "group" of 6 in parallel, then the 3 sets in series I would have effectively a 2g, 6 turn wire.
    I could do similar with 3 wires in parallel getting a total of 12 turns, or 2 wires in parallel getting 18 turns. Or possibly a single wire, with 36 turns.
    I hope you can see what I plan on doing.

    What I am most concerned about is creating what will basically amount to 3 terminal strips each with 6 connectors (could probably get away with terminal strips with less connectors and double up on some wires). I would also have to make some jumpers to allow the terminals to run in parallel/bridged (I've done this with flattened copper from very high quality copper pipe, put it between the base plate of the terminal - wire touches that and screw/press plate pushes down on all this to make contact).

    Can anyone think of why this wouldn't work or have suggestions on the build, warnings, etc? I would really love do this with some switches instead of having to unscrew stuff all the time.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,988
    745
    Better to use single solid copper wire enamelled, dont use multiple strands, what are you looking to make a welder, or just a variable output transformer?
     
  3. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4
    Variable output.

    All the strands are solid but there are 3 different color insulations making it easy to identify and I'm going to mark the end of each set of strands with a specific colored shrink tubing.

    So is the theory behind this ok and does the extra "slack" in the wire where the ends will be cause a problem (the slack is so I can manuever to the correct terminal) - most transformers have the wire pulled very tightly against the iron core. Now I'm only talking about 5mm most extra distance from the core than if it were pulled tight as a single wire.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,548
    2,373
    The winding method you describe is called bi-filar and is often done this way to keep parallel windings exactly equal.
    Keep the terminations as close as possible to the core.
    Max.
     
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  5. RichardO

    Well-Known Member

    May 4, 2013
    1,235
    384
    Whatever you do, don't stretch the Teflon insulation against a sharp corner. Teflon will creep over time and could cause a short.
     
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