UL 248-9:2010 free download Low-Voltage Fuses – Part 9: Class K Fuses
1 GeneralNOTE –
This Part is intended to be read together with the Standard for Low-Voltage Fuses – Part 1: General Requirements, hereafterreferred to as Part 1. The numbering of the Clauses in this Part correspond to like numbered Clauses in Part 1. The requirementsof Part 1 apply unless modified by this Part.For Clauses not shown below, reler to the Standard for Low-Voltage Fuses – Part 1:General Requirements，NMX-J-009/248/9-2000-ANCE CAN/CSA C22.2 No.248.1 ·UL248-1.,
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 K-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 12t 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, In， for each size is specified in this Part. Time-delay ratings are optional.
In Canada，250V ac fuses rated 15 – 60 A shall have a low melting point “P”(“D”for time delay)characteristic.See sub-clauses 6.1 and 9.2.
5 Characteristics
5.2 Voltage rating
For AC, the rating shall be 250 or 60o 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, 1 00,000, or 200,000 A
For DC, the preferred ratings are 1 0,000, 20,000, 50,000, 1 00,000, 1 50,000, 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.
8 Tests
8.2 Verification of temperature rise and current-carrying capacity
8.2.3 Test method
1 .0 I n – Temperature rise
1 .1 I n – Current-carrying capacity, I nf
8.2.3.1 Fuses rated 600 A or less
In addition to the requirements in Part 1 : At the conclusion of the temperature rise test, the test current shall be increased without interruption to 1 .1 I n for a period of not less than 1 5 min for fuses rated 0 – 200 A and not less than 30 min for fuses rated 201 – 600 A. Temperature is not to be monitored during this time.
8.2.4 Acceptability of test results
In addition to the requirements in Part 1 : The maximum temperature rise shall not exceed the following:
Contacts –
≤1 00 A – 55°C
>1 00 A – 75°C
8.3 Verification of overload operation
Part 1 , Table 4
Test 1 – 1 .35 I n
Test 3 – 2 I n
Test 5 – 5 I n for time-delay fuses only. For 250 V ac rated 30 A or less, the clearing time shall
be 8 s minimum.
UL 248-9:2010 free download
