Thermal value of fuse

1) The melting heat energy value (If2t) of the fuse refers to the energy value required for fuse fusing, which is usually used as the technical index of the fuse's ability to withstand surges, where I is the overload current, and t is the energy value (Ir2t) released when a surge occurs in the fuse time z circuit.

2) Principle: If2t>Ir2t must be considered when selecting fuse, that is, the melting heat energy of fuse shall be greater than the heat energy released by surge current.

3) The fusing time of the fuse is related to the heat generated by the current, heat dissipation conditions and thermal capacity characteristics of the fuse. Many factors will affect the fusing time of the fuse, so the fuse will have different If2t at different breaking current or time, that is, If2t is not a constant.

4) The energy/time curve best describes the change of the melting heat energy of the fuse, which is the main reference for designers when selecting the pulse resistance capability of the fuse.

5) Number of times of impulse impact resistance.

6) When If2t>Ir2t, the fuse should be able to withstand the impact of pulse, not be fused but will suffer some damage, so as to slightly reduce its If2t.

7) By calculating and selecting the relationship between If2t and Ir2t, we can know the number of pulses that the fuse can withstand. On the other hand, how many times the fuse needs to withstand the surge impact, we must select the relationship between If2t of the fuse and Ir2t of the circuit pulse

8) Approximate relationship between If2t and Ir2t of fuse

Ir2t<=30% If2t 100000 times

Ir2t<=38% If2t 10000 times

Ir2t<=48% If2t 1000 times