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Basic Transformer Question

Discussion in 'Electronic Basics' started by [email protected], Nov 15, 2005.

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  1. Guest

    I have a transformer with a 120V primary and a center tapped secondary,
    each side producing 51V. I can see 4 wires comming out of the
    secondary A, B, C, D where B & C are tied together forming the center
    tap. I want to get more current at 51V than each individual side can
    provide. Is there anything wrong with breaking the connection between
    B & C and connecting A&C together and B&D together to make the
    transformer into esentially a 120V primary, 51V secondary? I know I
    could just do it and see what happens, but this is a heavy duty
    transformer and I don't want to mess it up. Any advice would be
    greatly appreciated. Thanks
  2. Conceptually, there is nothing wrong with paralleling two similar
    windings to get a single output with a higher current capability.
    But, if one winding has any difference in turns count than the other,
    the slight difference in voltage will cause current to circulate
    through the two windings, heating them up.

    I would connect one pair of ends together and measure the voltage
    between the remaining pair of ends, to make sure that this voltage is
    essentially zero, before connecting those ends together.
  3. Pooh Bear

    Pooh Bear Guest

    Yes, you can do that.

    As John says though., you need to be sure that both windings are of exactly
    equal voltage ( i.e. the same number of turns ).

  4. Guest

    I tried it and it seems to be working ok. There is a small voltage
    difference of around .020V or 20mv. It doesn't seem to be causing any
    overheating or other problems.
  5. Pooh Bear

    Pooh Bear Guest

    That's fine. In practice the 2 windings won't be *exactly* the same
    voltage down to the millivolt level.

  6. Jasen Betts

    Jasen Betts Guest

    the safe way:

    disconnect B and C , measure the resistance between A and C (it should be
    infinite), if it isn't stop. connect A and C power it up and measure the voltage
    between B and D, it should be 0, if it is it's safe to connect them.

  7. Guest

    I hooked up a 7 amp load to the transformer last night and it is not
    even begining to show any signs of strain. I was using a DVOM with the
    10 amp AC setting. The DVOM was rated to function to 10A but the test
    leads that came with it were certainly not. Before I reallized what
    was happing, one of the test leads burt up. I don't think it hurt the
    DVOM though.
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