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Thread: Fuse "k" rating?

  1. #1
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    Aug 2010
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    Fuse "k" rating?

    Has anyone out there ever heard of a fuse "k" rating ? I am unfamilier with this term and I am wondering if they are refering to the actual interupting rating of the fuse and erroneously calling it a "k" rating instead. Any help out there to help me clarify this would be greatly appreciated.

  2. #2
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    Guide to Ampere Ratings, As taken form Eaton C-H

    “E” Designation: Fuses rated 100E or below will melt in 300 seconds at a current value between 2.0 and 2.4 times the E number. Fuses rated above 100E will melt in 600 seconds at a current value between 2.2 and 2.64 times the E number. If the current is higher than 2.4 or 2.64 times the E number, the user must consult the time-current curves for that particular fuse.

    “R” Designation: The fuse will melt in 15 to 35 seconds when the current equals 100 times the R number. If the current is higher than 100 times the R number, the user must consult the time-current curves for that fuse.

    “C” Designation: The fuse will melt in 1000 seconds at a current value, between 1.7 and 2.4 times the C number.
    If the current is higher than 2.4 times the C number, the user must consult the time-current curves for that particular fuse.

    “A” Designation: Fuses that do not comply with “E”, “R”, or “C” designations.

    Expulsion fuses can also be E-rated, K-rated and T-rated, and are also covered in the ANSI standards. The K and T ratings refer, respectively, to relatively “fast” and “slow” melting expulsion fuses. Detailed time-current tables would be needed to adequately define the ratings.

  3. #3
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    In low voltage fuses, Class K are Current Limiting fuses, with K-1 being the highest level and K5 being a little lower. There used to be a K-9 class but that is now obsolete.

    But because Class K fuse bodies are easily interchangeable with Class H which are not current limiting, most of the time we see them as Class RK-1 or RK-5, with the R being Rejection Clip style. So a Bussman LPN (250V) or LPS (600V) are Class RK-1 current limiting fuses, and the FRN/FRS are the Class RK-5 versions.

  4. #4
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    Quote Originally Posted by Jraef View Post
    There used to be a K-9 class but that is now obsolete.
    It used to be required for circuits installed in dog kennels:grin:

  5. #5
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    Quote Originally Posted by kwired View Post
    Originally Posted by Jraef
    There used to be a K-9 class but that is now obsolete.
    It used to be required for circuits installed in dog kennels:grin:
    I thought is was the dog that was being used as a fuse with indicator Arf Arf
    Wayne A. From: N.W.Indiana
    Be Fair, Be Safe
    Just don't be fairly safe

  6. #6
    Join Date
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    Quote Originally Posted by templdl View Post
    Guide to Ampere Ratings, As taken form Eaton C-H

    “E” Designation: Fuses rated 100E or below will melt in 300 seconds at a current value between 2.0 and 2.4 times the E number. Fuses rated above 100E will melt in 600 seconds at a current value between 2.2 and 2.64 times the E number. If the current is higher than 2.4 or 2.64 times the E number, the user must consult the time-current curves for that particular fuse.

    “R” Designation: The fuse will melt in 15 to 35 seconds when the current equals 100 times the R number. If the current is higher than 100 times the R number, the user must consult the time-current curves for that fuse.

    “C” Designation: The fuse will melt in 1000 seconds at a current value, between 1.7 and 2.4 times the C number.
    If the current is higher than 2.4 times the C number, the user must consult the time-current curves for that particular fuse.

    “A” Designation: Fuses that do not comply with “E”, “R”, or “C” designations.

    Expulsion fuses can also be E-rated, K-rated and T-rated, and are also covered in the ANSI standards. The K and T ratings refer, respectively, to relatively “fast” and “slow” melting expulsion fuses. Detailed time-current tables would be needed to adequately define the ratings.
    Very cool. Do you have a link to this CH document? I never felt like I understood the fuse ratings well enough.

  7. #7
    Join Date
    Aug 2010
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    2

    "k" rated fuses

    Thank's for the replies from everyone.I very much appreciate it.

  8. #8
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