Fuse Classification
1. Screw‑type Fuse (RL Series)
Its fuse cylinder is filled with quartz sand, in which the fuse element is embedded. When the element melts, the arc is projected onto the quartz sand and its interstices for rapid cooling and arc‑extinguishing. For status indication, one end of the fuse is fitted with a colour‑coded indicator dot; different colours correspond to different rated currents. The dot pops out once the fuse blows as a visual failure signal. Rated current ranges from 5 A to 200 A. It is mainly applied to branch circuits with high short‑circuit current or locations with flammable gas.
2.Filled‑cartridge Fuse (RT Series)
This is a current‑limiting type of fuse. It consists of a quartz‑sand‑filled ceramic fuse tube, contact parts and silver‑plated copper grid‑type fuse elements. It is mounted on a dedicated base, either with an isolating switch disconnector or where the fuse itself serves as the isolating knife, operated via a manual mechanism. Rated current: 50 A‑1000 A. Suitable for circuits with high short‑circuit current and flammable‑gas‑hazardous areas.
3. Non‑filled Cartridge Fuse (RM Series)
Its fuse tube is made of fibre material, fitted with zinc‑alloy fuse elements of variable cross‑section. Upon melting of the element, heat decomposes part of the fibre tube to generate high‑pressure gas, which quenches the arc rapidly. Featuring simple construction, reliable protection and easy operation, this fuse is generally assembled together with knife‑blade switches.
4. Filled Enclosed High‑speed Fuse (RS Series)
A fast‑acting fuse assembled with fuse tube, contact base, trip indicator and fuse element. Its element adopts special cross‑section or mesh structure and is disposable (non‑replaceable). Thanks to ultra‑fast response, it is widely used for protection of semiconductor rectifier components.
5. Fuses can be classified by operating voltage into high‑voltage fuses and low‑voltage fuses.
By protected objects: fuses for transformers and general electrical equipment, fuses for voltage‑transformer protection, fuses for power‑capacitor protection, semiconductor‑element protection fuses, motor‑protection fuses and household‑appliance protection fuses.
By construction: open‑type, semi‑enclosed, cartridge‑type and expulsion‑type fuses.
6. Open‑type Fuse
Simple‑structure design. The fuse element is fully exposed to ambient air and supported by porcelain posts. Designed for outdoor low‑voltage applications. Noticeable acoustic and light effects occur during current interruption in open air.
7. Semi‑enclosed Fuse
The fuse element is mounted on a porcelain frame and inserted into a porcelain box with metal sockets at both ends. Intended for indoor low‑voltage service. The porcelain enclosure suppresses noise and flashover light during interruption.
8. Cartridge‑type Fuse
The fuse element is housed inside a fuse cartridge, which is fitted onto a base or directly connected into the circuit. The cartridge is a fully sealed insulating tube with metal end caps or contact knives.
- When filled with quartz sand, it delivers current‑limiting performance during breaking and achieves high breaking capacity, also known as high‑breaking‑capacity fuse.
- Vacuum‑filled variants are vacuum fuses.
- SF₆‑gas‑filled versions are SF₆ fuses for enhanced arc‑quenching performance.
Benefiting from superior insulating properties of quartz sand, vacuum and SF₆ gas, cartridge‑type fuses are available for both low‑voltage and high‑voltage systems.
9. Expulsion‑type Fuse
The fuse element is housed inside an insulating tube made of gas‑generating solid material (electrical pressboard or acrylic material). When short‑circuit current flows through, the element melts instantly and forms an arc. The high‑temperature arc decomposes the gas‑generating material rapidly to produce large volumes of high‑pressure gas, expelling ionised gas together with the arc out of both tube ends accompanied by loud noise and flash. The arc extinguishes at AC current zero‑crossing to complete circuit interruption.
The insulating tube is assembled on an insulating support to form a complete unit. In many designs, the upper end of the tube is hinged, and the tube drops down after fault clearing. Such expulsion‑type fuses are commonly referred to as drop‑out fuses.