Bussmann 125A Fast Acting Ceramic High Speed Semiconductor Fuses with 500VAC/DC Voltage Rating; FWH Series

Fast-acting, nonindicating semiconductor fuses open within seconds of being exposed to overloads and short circuits. Also called fast-blow semiconductor fuses, they are highly sensitive to changes in current flow and don't tolerate temporary overload currents or power surges. They have no indicator for identifying a blown fuse, so they're sometimes used with an indicating fuse block or cover.

Semiconductor fuses provide overcurrent protection for solid-state components such diodes and thyristors in variable-speed drives, power rectifiers, uninterruptible power supplies (UPSs), and other power electronics applications. Also known as rectifier fuses, they are extremely current-limiting to prevent electrical damage by disconnecting circuits before they're exposed to the full magnitude and duration of an overcurrent.