W-F-18140
3.5.1 Mounting. Unless otherwise specified (see 3.1), the fuse shall be designed for use in fuseholders in accordance with UL 4248-1 and permit convenient insertion and removal from fuseholders without the use of special tools.
3.5.2 Terminals. Terminals shall be secured to the fuse body so that they will not loosen. The fuse element shall be attached to the terminals so that there will be no danger of breaking the fuse element or connections when installing the fuse. Fuses with knife blade terminals shall be aligned so that their planes are within 4 degrees of each other. The alignment shall be insured by means other than friction.
3.5.3 Ferrule alignment. Fuses with ferrule terminals shall pass through a tubular gauge having a length not less than that of the fuse. The tubular gauge shall have an internal diameter 0.005 inch greater than the maximum ferrule diameter for fuse lengths up to and including 1.75 inches. For fuse lengths greater than 1.75 inches, the tubular gauge shall have an internal diameter 0.010 inch greater than the maximum ferrule diameter.
3.5.4 Terminal finish or plating. Ferrules, knife blades, lugs, or other terminals shall be finished (plated, dipped, coated) or shall be natural (no finishing process), as specified (see 3.1). Finish shall be optional when not specified.
3.5.4.1 Silver plating (see 3.1). Silver plating shall be in accordance with ASTM 8700 or equivalent as approved by the qualifying activity, and shall be 99.9 percent pure silver, not coin silver. It shall be not less than .00008 inch (0.002 mm) inch thick. When silver plating is specified, the letter "S" shall be added as a suffix to the end of the Government part number.
3.6 Terminal strength. When tested as specified in 4.7.2, fuse terminals shall not loosen or become damaged.
3.7 Current carrying capacity. When tested as specified in 4.7.3, fuses shall carry the specified percentage of current indefinitely (see 3.1). The temperature of the body shall at no point rise more than the amount specified (see
3.1).
3.8 Watts loss (when specified, see 3.1). When fuses are tested as specified in 4.7.4, the watts loss shall be as specified (see 3.1).
3.9 Overload interrupt. When tested as specified in 4.7.5, fuses shall open the circuit within the time specified (see
3.1) without causing the case or body to char, fracture, or otherwise sustain physical damage. Time delay or dual element fuses shall not open the circuit faster than specified (see 3.1).
3.9.1 Opening at rated voltage. When tested as specified in 4.7.5.1 classes G, J, K, and R fuses shall open the circuit without causing the case or body to char, fracture, or otherwise sustain physical damage.
3.10 Interrupting capacity rating. When fuses are tested as specified in 4.7.6 the interrupting capacity shall be not less than specified (see 3.1). The fuse shall remain intact and permanently open the circuit and shall not ignite cotton, emit molten solder, or permit movement or deformation of either or both end-caps.
3.11 Threshold ratio (when specified, see 3.1). When tested as specified in 4.7.7, the fuses shall clear the circuit in the first half cycle after the circuit is closed. The maximum threshold ratio for the fuse shall be as specified (see
3.1).
3.12 Peak let-thru current. When fuses are tested as specified in 4.7.8 , the peak let-thru current shall not exceed the limit specified (see 3.1).
3.13 Maximum clearing I2T. When fuses are tested as specified in
4.7.9, the amount of ampere-squared seconds passed by the fuse during melting, arcing, and clearing shall not exceed the value specified (see 3.1).
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