IR rating

This topic contains 3 replies, has 2 voices, and was last updated by John C John C 10 months, 1 week ago.

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  • #8184

    Pete Howard
    Participant

    Ok wanted to know about the IR rating on the side of my fuses.
    What does IR = 200KA mean?


  • #8185
    John C
    John C
    Galco Representative

    Hello Pete, the IR rating is a great question.

    If your fuse has a 200KA IR rating on it then it sounds like it is a slow blow or time delay type fuse. I was actually just looking at a fuse that has a 300KA rating.

    So this is the Interrupting Rating, or you could say the Instant Rating. If it says 200KA on it, then it takes 200,000 amps to blow that fuse instantly, no delay at all.

    Fast acting fuses or “Semiconductor fuses” have some of the fastest ratings about 10KA or 10,000 amps Interrupting Rating.
    Oddly enough, fuses have all different load ratings such 10 amp, 100 amp or 500 amp all with the same interrupting rating if they are the same type. Fuses are a bit of a science onto their own, eh?


  • #8186

    Pete Howard
    Participant

    What are the different types used for?
    I mean what the heck could you need 300,000 amps for?


  • #8187
    John C
    John C
    Galco Representative

    Well the Semiconductor fuses with the lower rating of 10KA are for protecting things like Rectifiers and Transistors connected to the line power source in a building.

    Time delay fuses are for things like starting an electric motor connected directly to the line with a contactor. Motors pull up to 600% of name plate rating for a few seconds, larger motors take longer, high inertia takes even longer maybe minutes to get up to speed and drop the load amps below motor name plate FLA.


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