Everyone will always see some names about chip fuses on chip fuses. In fact, these are all terms about chip fuses, so what do these terms mean?
1. Voltage rating:
The voltage rating of the fuse is a value compared with the voltage in the circuit, it must be greater than or equal to the voltage in the circuit, so that the circuit safety can be guaranteed. Therefore, the voltage rating series of chip fuses are: 24V, 32V, 48V, 63V, 125V.
2. Ambient temperature:
The fuse is a temperature sensitive element. The experiment of its current carrying capacity was carried out under the environment of 25 ℃. The higher the ambient temperature, the higher the operating temperature of the fuse, the lower the corresponding current carrying capacity, and the shorter the life. Conversely, the lower the ambient temperature, the longer the life of the fuse.
3. Normal working current:
Under the condition of 25 ℃, the rated current value of the fuse should generally be reduced by 25% to avoid harmful blowing. The material of most fuses has a lower melting temperature. Therefore, the fuse is more sensitive to changes in ambient temperature. For example, at a 25 ° C ambient temperature, a fuse with a current rating of 1A cannot normally work in a circuit with a steady-state current greater than 0.75A. (Related reading: How to choose a chip fuse)
4. Fuse rated capacity:
Also called breaking capacity. The rated fusing capacity is the maximum allowable current that the fuse can surely blow at the rated voltage. During short circuit, instantaneous overload current larger than normal working current will be passed through the fuse many times. Safe operation requires the fuse to remain intact (without bursting or breaking).
The resistance of the fuse will have a few ohms for the resistance of a fuse with an amperage of less than 1, so this problem should be considered when using a fuse in a low-voltage circuit. Most fuses are made of positive temperature coefficient materials, so there are also cold resistance and thermal resistance. At other times it seems less important.
6. Nominal melting heat energy:
Refers to the energy required to melt the fuse part, expressed by I2t, read as "ampere square seconds". Generally, an authoritative certification body should conduct a melting heat energy test: apply a current increase to the fuse and measure the time when melting occurs. If melting does not occur within about 0.008 seconds or longer, then increase the intensity of the pulse current. Repeat the experiment until the fuse blowing time is within 0.008 seconds. The purpose of this test is to ensure that the generated thermal energy does not have enough time to run away from the fuse component through thermal conduction, that is, all the thermal energy is used to blow the fuse.
Therefore, when choosing a chip fuse, everyone should consider the normal operating current, fault current, I2t value, ambient temperature, internal resistance, and rated value reduction.