5kV BOLT-IN FUSES Amp-trap Bolt-in Series E-rated fuses are single, double or triple barrel (3" diam.) with end mounts designed for bolting directly to equipment bus or terminal pads. They are UL listed and are for use indoors (or outdoors in a weatherproof enclosure). The unique time-current characteristic of Ferraz Shawmut 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. Bolt-in fuses are typically sized at transformer rated current of 133%, thereby providing superior overall protection.