UL 248-9:2000 pdf download Low-Voltage Fuses – Part 9: Class K Fuses
1.1 Scope
This Part applies to Class K fuses rated 600 A or less and either 250 or 600 V ac. DC ratings are optional
4 Classification
Class K fuses are non-renewable, with interrupting ratings of 50,000, 100,000, or 200,000 A. Class kfuses are divided into sub-classes K-1, K-5. and 9 which are physically interchangeable with each other(and Class H fuses) for the same current and voltage ratings. Each sub-class has specified limits of peaklet-through current and clearing 1t characteristics. K-1 has the lowest limits (most current-limiting), K-5higher, and K-9 highest. Each of the voltage ratings, 250 and 600 V ac, is divided into six body sizes. Themaximum current rating, ln, for each size is specified in this Part, Time-delay ratings are optional.
5 Characteristics
5.2 Voltage rating
For AC, the rating shall be 250 or 600 V ac in accordance with dimensions shown in Figure A. The DCvoltage rating may be different from the AC rating.
5.3 Current rating
Refer to Figures A and B for range of current ratings in each body size for each voltage rating
5.5 Interrupting rating
For AC – 50,000,100,000,or 200,000 A
For DC, the preferred ratings are 10,000, 20,000, 50,000, 100,000, 150,000, or 200,000 A.
5.6 Peak let-through current and clearing I 2 t characteristics
Maximum values of peak let-through current and clearing I 2 t for 250 and 600 V ac, Class K-1 , Class K-5,and Class K-9 fuses are given in Tables A and B.
6 Marking
6.1 Marking of fuses
g) The fuse shall not be marked ″Current Limiting.″
7 Construction
7.1 Dimensions
Fuse dimensions are shown in Figures A and B.

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