5kV FERRULE MOUNTED FUSES Amp-trap CS-3, 9F60 and 9F62 E-Rated 5kV fuses have 2 or 3 Inch diameter barrels with ferrules and are mounted in spring reinforced clips. Some are UL listed as "general purpose current-limiting fuses" and some are for outdoor use. The unique time-current characteristic of Mersen E-Rated fuses allows them to be closely sized to transformer full-load rated current, as recommended by IEEE guidelines, without being affected by normal magnetizing inrush current. fuses are typically sized at transformer rated current of 133%, thereby providing superior overall protection.