Basic knowledge of current fuse application

Function of fuse:

1. Under normal conditions, the fuse plays the role of connecting the circuit in the circuit.

2. Under abnormal (overload) conditions, the fuse is used as the safety protection element in the circuit to safely cut off and protect the circuit through its own fusing.

2、 Working principle of current fuse:

When the fuse is energized, the heat converted by electric energy can increase the temperature of the melt. When the normal working current or allowable overload current passes through, the heat generated can be radiated to the surrounding environment through the melt and shell, and the heat radiated by convection, conduction and other means can gradually balance with the heat generated. If the heat generated is greater than the heat dissipated, the excess heat will gradually accumulate on the meltable to increase the melt temperature; When the temperature reaches or exceeds the melting point of the meltable, the meltable will melt and fuse and cut off the current, which plays the role of safety protection circuit.

3、 Classification of current fuses:

1. It is divided into: φ 2、 φ 3、 φ 4、 φ 5、 φ 6 and others.

2. According to the fusing characteristics, it is divided into: fast fusing type, medium delay fusing type and delay fusing type. (it can also be divided into express, strong and delayed).

3. According to the breaking capacity, it can be divided into low breaking type and high breaking type (it can also be divided into enhanced breaking type).

4. It can be divided into UL / cul (North America), IEC (China, Europe, etc.) and MIT / KTL (Japan / Korea) according to safety standards (or regions of use).

In many electronic devices, fuse is indispensable. Since Edison invented the first plug-in fuse that sealed the thin wire in the lamp holder in the 1990s, there are more and more kinds of fuses and their applications are more and more widely. Here are some fuse parameters, selection and application common sense.

The rated values and performance indexes of fuses are determined according to laboratory conditions and acceptance specifications. There are many authoritative testing and appraisal institutions in the world, such as UL certification of underwriter experimental company in the United States, cul certification of Canadian Standards Association, MTTI certification of Japan's Ministry of international trade and industry and ice certification of International Electrical Technical Committee.

1 factors involved in fuse selection

a. Normal operating current.

b. The applied voltage applied to the fuse.

c. An abnormal current that requires the fuse to open.

d. The shortest and longest time allowed for abnormal current.

e. The ambient temperature of the fuse.

f. Pulse, impulse current, surge current, starting current and circuit transient value.

g. Whether there are special requirements beyond the fuse specification.

h. Dimensional limitations of the mounting structure.

i. Required certification authority.

j. Fuse holder: fuse clip (divided into current fuse clip and automobile fuse clip, which shall be selected according to the actual situation), installation box, panel installation, etc.

5. Other classifications.