Overloads and fuse design

Discussion in 'General Electronics Chat' started by sunshine03, Jun 9, 2008.

  1. sunshine03

    Thread Starter New Member

    Dec 30, 2007

    I have a couple of questions dealing with fuses and their design ........
    Is it true that automotive fuses are designed to withstand start up current spikes high above their amperage rating-without blowing the fuse?
    Also, if a worn out component operates at or just under max amperage,can it cause it's fuse, the fuse box and joining wires to melt and burn without actually blowing the fuse and opening the circuit?

    I really appreciate your time and help
  2. beenthere

    Retired Moderator

    Apr 20, 2004
  3. gotumal

    Active Member

    Mar 24, 2008

    Roughly there are two types of fuses. Slow blow and fast blow. You need to check for the type of load. If that is inductive, your fuse should wait for inrush curent to flow. But should blow before your load gets damaged.
    You can find out the energy with time and current. Visit Little fuse web site, you would find very informative documents.
  4. sunshine03

    Thread Starter New Member

    Dec 30, 2007
    According to the websites,both statements are true ...........
    1-Automotive fuses are slow-blow and designed to withstand very high start up surges
    that pass quickly
    2-A fuse runs hotter as the normal operating current approaches or exceeds the current
    rating of the selected fuse....(fuses)....should last indefinitely if operated at no more
    than 75% of fuse ampere rating
    (loose fuse holders over heat fuses to)

    Thanks for all the great info