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8983 Views 2 Replies Latest reply: Mar 3, 2012 8:09 AM by tedcs RSS
Currently Being Moderated

Feb 28, 2012 8:31 AM

Why multiple wires for same voltage?

Some one asked me this question and I thought I would pass it on.

Why do computer manufactures provide multiple wires for the same voltage. For example, some power supplies have three wires for the 12-V connection.

  • lieser Novice 2 posts since
    Feb 28, 2012
    Currently Being Moderated
    Feb 28, 2012 6:19 PM (in response to EPaul)
    Why multiple wires for same voltage?

    Briefly:  current carrying capacity without undue voltage drop. 

     

     

    Every wire has some resistance even a relatively short 12 gauge wire used in a computer PS.  So given ohms law V=IR, there will be some voltage drop across that wire that increases with increasing current.  Motherboards in particular can be very power hungry and are not very tolerant of voltage variation.

     

    The solution is to reduce the resistance in the path from the PS to the MB or other peripheral.  The simple way is the have multiple wires.  All those wires connect to the same bus within the PS.

  • tedcs Novice 4 posts since
    Mar 3, 2012
    Currently Being Moderated
    Mar 3, 2012 8:09 AM (in response to EPaul)
    multiple wires for the same voltage?

    EPaul; from a mechanical/manufacturing standpoint:

    Multiple small wires may be more practical to attach to printed circuit boards and connectors than large gauge wire.

    The connection of several small wires may be more reliable than a single larger gauge wire.

    Small wires are more flexible than a single large conductor.

    It is less costly to purchase and stock a zillion feet of small wire than many different gauges of wire.

     

    Too, in some instances, multiple small conductors have electrical characteristics that are

    somewhat different from those of a single larger conductor. The difference may be significant

    and advantageous from an electrical standpoint.

     

    In a computer power supply, minimized manufacturing cost and maximized reliablility

    are probably the reason for multiple wires for the same voltage.

     

    Everything I know is wrong.

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