Fuse "k" rating?

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logan123

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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.
 
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templdl

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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.
 
Jraef

Jraef

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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.
 
steve66

steve66

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Location
Illinois
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Engineer
templdl said:
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.
Click to expand...

Very cool. Do you have a link to this CH document? I never felt like I understood the fuse ratings well enough.
 
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