The biggest safety fuse current fuse

The fuse is electronic protection device, its function is to protect circuit, avoid electronic equipment and personal safety damage, qualified fuse will cut off the circuit in circuit fault when fusing itself, as well as any time after the blown fuse can guarantee unsafe phenomenon does not occur. The biggest safety fuse fuse current is also called the rated breaking capacity, according to the international standard definition: current fuse in the rated voltage under load, the maximum current value can safely to cut off the circuit.

Fuse breaking ability of its protection function and supporting function have no effect, but for the fuse of the vital safety function. In the select the fuse specifications, there is a principle is rated breaking capacity must be greater than or equal to the largest protection circuit in the case of short circuit current.

Limited due to the rise of temperature of the current through the fuse itself, can guarantee the normal work of the fuse safety; The fuse blown fuse voltage is greater than or equal to the rated voltage circuit can guarantee after pressure; And fuse fusing process is one of the biggest energy release process, select the breaking capacity of enough to enable the fuse throughout the process of releasing energy does not produce any unsafe phenomenon, so as to ensure the whole process of fusing is absolutely safe.

In be used actually has one kind of phenomenon, when short circuit current exceeds rated breaking capacity of the fuse, appeared the following conduction, continuous arcing, again burst into flames, the phenomenon such as fuse burst, tears splash, serious still can cause the personal safety. International standards by the international electrotechnical commission (IEC60127-1 the definition of "small fuse and general requirements") specified in the test fuse breaking ability of several conditions, is to ensure the safety of the fuse is very important to the index, specific as follows:

Rated ac power supply, power supply impedance is less than 10% of the total impedance circuit;

30 degrees phase after zero voltage switching;

Final keep recovery voltage (1 ~ 1.05 times rated voltage) 30 seconds;

After the test the insulation resistance of not less than 0.1 megohm;

Throughout the process does not appear the unsafe phenomenon.

Breaking ability of the classification of the circuit, the fuse is also divided into ac and dc two indicators, under normal circumstances, the harshness of dc is higher than ac. Some fuse is ac/dc, it must be a separate ac/dc breaking ability indicators, in line with international standards of fuse breaking ability of the common specifications of products are as follows:

Tubular fuse: high breaking - in - 1500 - a, 150 a, low - 35 a or 10 times the rated current (whichever)

Insert fuse: 50 a, 35 a or 10 times the rated current (between)

SMD fuse: ac dc - 50-100 - a, a, 35 a or 10 times the rated current (whichever)

Above you can see the fuse breaking ability had no direct connection with its performance, but closely associated with circuit safety, for engineers, when considering the overall circuit safety, must consider fuse block ability, this is an important part of the overall circuit protection.