Electrical Fuse
Having to disappear in favor of the circuit breaker, the electrical fuse nevertheless has certain advantages. What is the fuse used for, what are its different types and what are its disadvantages compared to the circuit breaker? We take stock here in the context of our file on the various elements of the electrical installation.
Definition and principle of use
The fuse or fuse circuit breaker is a safety device designed to cut off the electric current in the event of an overload or a short circuit (see our article on the role of the fuse here). The main component of this device is a small insulator enveloping a conductive wire which melts when it is crossed by a current of intensity greater than the supported caliber. Thus, it makes it possible to open the electrical circuit during a period of overcurrent and prevents fires as well as the destruction of the entire system. The fuse guarantees the integrity of the power supply circuit.
Fuse type and manufacturing standards
Fuses are visible in almost all old electrical installations. The operation of these devices is governed by standard IEC 60269. This standard regulates three modes of operation:
• gG fuse: very common in domestic installations, it provides protection against short circuits and overloads.
• aM fuse: only used against short circuits, for example in motors and primary circuits of transformers.
• Ultra-fast fuse: designed to protect semiconductors.
There are different types of fuses depending on their shape and format. Generally, a fuse takes the form of a ceramic cylinder (especially for electronic circuits) or glass (on electrical panels, inside sockets, etc.), the center of which is crossed by a metal filament .
There are other types of fuses such as those with tabs or those with strips. The latter are mainly installed on the starting systems of automobiles. Finally, some recent fuses incorporate an explosive component that bursts when the current intensity is too high.
According to the IEC 60127 standard, manufacturers of electrical components allocate fuses according to the time that these devices take to interrupt the current. Thus, FF (ultra-fast), F (fast), T (delay) and TT (ultra-delay) fuses are found on the market. There are 2 A, 10 A, 16 A or 32 A fuses on the market. 10 A fuses are sufficient to operate and protect lighting systems. However, for a three-phase socket or an oven, it is necessary to have 16 or 32 A fuses.
Between fuse and circuit breaker
Fuses have the disadvantage of only being used once. So, if your fuse blows, it must be replaced with a new one. Also, for some types of fuses, the wire is not visible. In the event of a power cut, it is necessary to test them one by one to determine if one of them is responsible for the opening of the circuit. On the other hand, the circuit breakers are resettable at will and reusable. These correspond to switches designed to break the circuit when the intensity of the current exceeds the limit threshold.
How does a fuse work?
The fuse contained in your electrical panel is used to protect against electrical overcurrents and short circuits. It owes its name to the fusion of the filament it contains. This filament conducts electricity and melts in the event of an overcurrent, as this increases the temperature. By melting, the electrical circuit is said to be “open”, which brings the electrical intensity to zero, thus protecting your home.
After melting, the fuse must be changed, which means buying new ones regularly to have some on hand in case of an electrical problem.
Color coding and current ratings torpedo fuses
| 5A | 8 A | 10A | 16A | 25A | 40A |
|---|---|---|---|---|---|
| yellow | White | green | red | blue | Gray |
Color coding and current ratings of automotive blade fuses
| 1A | 2 A | 3 A | 4 A | 5A | 7.5A | 10A | 15A | 20A |
|---|---|---|---|---|---|---|---|---|
| black | Gray | violet | pink | light brown | brown | red | blue | yellow |
| 25A | 30A | 40A | 50A | 60A | 70A | 80A | 100A | |
| frosted | blue green | orange | red | blue | light brown | clear | violet | |
Stripe fuses
Consist of a stamped strip of sheet metal fuse.
| DIN 72581-2 | DIN 43560-1 | |
| length | 41mm | 82mm |
|---|---|---|
| Broad | 11mm | 20mm |
| contact spacing | 30mm | 60mm |
| contact opening | 5.5mm (M5) | 11mm (M10) |
| rated current | 30, 50, 80, 100A | 35, 50, 63, 80, 100, 125, 160, 200, 250, 300, 355, 425A |
| Tripping time (minimum) | 1 hour at 1.3× IN | up to 200 A: 1 hour at 1.5 × I N 250 to 425 A: 1 minute at 1.6 × I N |
| trip time (maximum) | 1 minute at 2.5× IN | 1 minute at 2.2× IN 0.8 to 10 seconds at 2.5× IN 0.2 to 2 seconds at 4.0 × IN |
| voltage drop | maximum 80 mV |
The benefits of fuses
Although a fuse can only be used once and cannot be reset like a circuit breaker, it has certain advantages. Indeed, it is very compact and its purchase requires less financial investment compared to a circuit breaker. Its installation is also quite simple!
Sources: PinterPandai, TokoPinter, Circuit Globe, Battle Born Batteries
Photo credit: Medvedev (CC BY-SA 3.0) via Wikimedia Commons
Photo description: 5 different sizes of insert fuses (from left to right):
5×20 mm
6×30 mm
6,3×32 mm (¼ × 1¼ inch)
6,3×40 mm
10×34,9 mm
