The high-speed fuse is assembled with a ceramic enclosure, conductive plates, fuse element, quartz sand, arc suppressant and indicator. Its fuse element is manufactured from pure silver and shaped as rectangular thin sheets designed with narrow, holed necks.

Pure silver boasts low resistivity, favorable ductility and outstanding chemical stability. These properties allow the fuse element to be processed into thin sheets adopting the structure of narrow necks with circular holes. When a short-circuit fault emerges, the narrow necks bear elevated current density and melt in priority. The resulting electric arc is broken into many segments by quartz sand. Divided arcs carry smaller current and occupy confined space, so they can be readily absorbed by the arc suppressant. Since quartz sand serves as an insulating material, an insulating barrier forms right after arc extinction to isolate the circuit.

Inverse-Time Current Protection Characteristic

High-speed fuses adopt inverse-time protection performance. To be specific, low overload current leads to longer fusing duration, while greater overload current shortens the fusing time. The fuse can remain intact and operate continuously within the defined scope of overload current and lasting time. A variety of fusing characteristic curves are available for fuses to match different types of protected equipment.

Current-Limiting Characteristic

The fuse element of a high-speed fuse consists of rectangular thin sheets fitted with successive narrow holed necks, and quartz sand fills the inner cavity as the arc-extinguishing medium. These narrow holed necks feature tiny cross-sectional area and low thermal capacity. Upon short-circuit failure, the necks melt before the fault current reaches the peak of prospective short-circuit current, and the arc is split into multiple sections by quartz sand. This mechanism suppresses the growth of short-circuit current and speeds up arc extinction simultaneously.

Superior Breaking Capacity

During short-circuit incidents, the narrow holed necks melt first, and the arc is segmented into small parts and extinguished rapidly. Benefiting from the insulation property of quartz sand, the fuse becomes an insulator immediately once the arc vanishes to disconnect the circuit. Hence, high-speed fuses deliver excellent breaking capacity with a maximum rating of 50 kA.

Reduced Impact Energy on Load Equipment

In case of circuit short-circuit faults, the impact energy sustained by load equipment complies with the formula:

W=I²RT

Where:

I — Short-circuit current

R — Circuit resistance

T — Time from short-circuit emergence to circuit disconnection