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Fuses in parallel

Discussion in 'General Discussion' started by mnewman, Jan 22, 2012.

  1. mnewman Junior Level

    When an arcing fault occurs downstream from two 100A fuses in parallel, can the fuses modelled by a single 100A fuse by shifting the current axis to the right by a factor of two to represent the time-current curve for the two parallel 100A fuses ?
    The above assumes that the current divides equally between the two 100A parallel fuses.
    mnewman, Jan 22, 2012
    #1

  2. brainfiller Administrator

    What voltage? Medium Voltage fuses have a parallel mounting for larger ratings. i.e. 540E which is made up of 2 - 300E fuses in parallel. 540E = (2 x 300E) x 90% The curve is specific for a 540. I did not overlay a shifted 300E TCC with a 540E but it looks like the shapes are similar.

    In the U.S. we don't parallel LV fuses (except perhaps cable limiters on networks)
    brainfiller, Jan 24, 2012
    #2

  3. PaulEngr Sparks Level

    There is a small problem with this. The average fuse rating doubles but the fuse accuracy goes down. Fuse curves show a range of values to accomodate a +/-% factor. If you parallel them, you might get a batch which are both on the extreme to either the positive (bad from an arc flash point of view) or negative side.
    PaulEngr, Jan 28, 2012
    #3

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