UL 248-12:2018-01 Low-Voltage Fuses – Part 12: Class R Fuses

UL 248-12:2018-01 Low-Voltage Fuses – Part 12: Class R Fuses. This Part applies to Class R fuses rated 600 A or less and either 250 or 600 V ac. DC ratings are optional. 4 Classification Class R fuses are non-renewable and current-limiting, with an interrupting rating of 200,000 A. Class R fuses are divided into sub-classes RK1 and RK5 and are physically interchangeable for the same current and voltage ratings. Class RK1 fuses have lower specified maximum peak let-through current and clearing l2t characteristics. Each of the voltage ratings, 250 and 600 V ac, is divided into six body sizes. The maximum current rating, I,,, for each size is specified in this Standard. 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 Figures A and B. The DC voltage 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, 200,000 A, or 300,000 A at the manufacturer’s option (300,000 not applicable in Mexico). For DC, the preferred ratings are 10,000, 20,000, 50,000, 100,000, 150,000, 200,000, or 300,000A. 5.6 Peak let-through current and clearing 12t characteristics Maximum values of peak let-through current and clearing l2t Class RK1 and Class RK5 fuses are given in Table A (see 8.5.3). Peak let-through currents shall not exceed the levels defined by the appropriate Let Through Function specified in Table A, as verified through measurement of peak let-through currents at 25, 50, 100, 200, and, if applicable, 300 kA. Clearing l2t values recorded shall not exceed the limits specified in Table A as verified through measurement of clearing l2t values at 25, 50, 100, 200, and, if applicable, 300 kA. 8.5 Verification of peak let-through current and clearing 12t characteristics 8.5.3 Acceptability of test results Peak let-through currents shall not exceed the levels defined by the appropriate Let Through Function specified in Table A, as verified through measurement of peak let-through currents at 25, 50, 100, 200, and, if applicable, 300 kA. Clearing l2t values recorded shall not exceed the limits specified in Table A as verified through measurement of clearing 121 values at 25, 50, 100, 200, and, if applicable, 300 kA.UL 248-12 pdf download.