The first function of the fuse is the protection function. In general, the rated current of the fuse must be greater than the normal working current of the circuit, and it has a certain overload capacity, but the margin cannot be too large.
The second function of the fuse is the load-bearing function, which is what is usually called the pulse resistance capability. During the use of the fuse, the chance of normal current fluctuations or instantaneous pulses is much greater than that of fault overcurrent. This consideration is particularly important for the use of the fuse.
The third function of the fuse is a safety function. A high-quality and reliable fuse should ensure safety before, during and after its action, that is, it is safely conducted and melted safely. In summary, proper fusing characteristics and rated current; adequate and reasonable melting heat value; and proper breaking capacity, rated voltage and safety certification are necessary conditions to ensure the main functions of the fuse.
Other factors that affect the performance of the fuse:
1. The internal resistance of the fuse: the increase of the initial internal resistance or the increase of the internal resistance after the fuse is aging will lead to changes in the heat dissipation conditions of the fuse, which will make the fuse's fusing time faster;
2. The connection of the fuse: The reliable connection of the fuse in the circuit is an important part of ensuring the performance of the fuse. If the contact resistance of the connection part increases, the consequence is the same as the increase of the internal resistance;
3. Surrounding heat dissipation conditions: the distance between the fuse and the heating element, the density of the components in the circuit, the cross-sectional area and length of the connecting wire or the wiring on the PC board are all related;
For small-size fuses, if their internal resistance is large and the working voltage is very low, sometimes there will be no current output. This is not a problem with the fuse, but caused by other external factors.
In addition, improper selection of the fusing characteristics, rated current, rated voltage, and breaking capacity of the fuse technical parameters will definitely affect the normal function of the fuse.
