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The first function of the fuse is to protect the function. In general, the rated current of the fuse must be greater than the normal working current of the circuit, and has certain overload capacity, but the residual amount cannot be too large.
The second function of the fuse is the carrying capacity, which is commonly referred to as the impulse resistance. In the process of using the fuse, the chance of normal current fluctuation or instantaneous pulse is much more than the fault current, which is especially important for the use of fuses.
The third function of fuse is safety function. High quality and reliable fuse should be able to ensure safety before and after the action, namely safe conduction and safe fuse. In summary, the appropriate fuse characteristics and rated current; Sufficient and reasonable melting heat value; And proper breaking capacity, rated voltage and safety certification are necessary to ensure the main function of fuse.
Other factors affecting the performance of fuses:
1. Internal resistance of fuses: the increase of initial internal resistance or the increase of internal resistance after the aging of the fuse will result in the change of the fuse cooling condition, which will make the fuse time of fuse become faster.
2. Connection of fuse: the reliable connection of fuse in the circuit is an important link to ensure the performance of the fuse. If the contact resistance increases, the effect will be the same as that of the internal resistance.
3. Ambient heat dissipation conditions: the distance between the fuse and the heating element, the degree of arrangement of the components in the circuit, the cross-sectional area and length of the connecting wire or PC board;
For small size fuse, if its internal resistance is larger, and the working voltage is very low, can appear sometimes the phenomenon of output current, this is not the fuse has a problem, but other factors caused by the outside world.
Besides, improper selection of fuse characteristics, rated current, rated voltage and breaking capacity of fuse technology will also influence the normal function of fuse.