Bussmann 40A Time Delay Melamine Fuse with 600VAC/300VDC Voltage Rating; LPJ Series

Time-delay, nonindicating UL Class J fuses tolerate temporary inrush currents without opening, which prevents nuisance-blowing from motor and equipment startups. Also called slow-blow Class J fuses, they open to disconnect an electrical circuit when exposed to sustained loads and short circuits. They have no indicator for identifying a blown fuse, so they're sometimes used with an indicating fuse block or cover.

UL Class J fuses have a high interrupting rating for protecting against short circuits and are ideal for IEC motor starter applications. These 600VAC fuses are not interchangeable with any other UL fuse class. They are current-limiting to prevent electrical damage by disconnecting circuits before they're exposed to the full magnitude and duration of an overcurrent.