The carrying capacity of the fuse, which is commonly referred to as the impulse resistance, is an important parameter that we must consider when selecting the fuse. In the process of using the fuse, the chance of normal current fluctuation or instantaneous pulse is much more than that of fault overcurrent, so in a sense, this consideration is particularly important and more practical for the use of the fuse.
As long as the melting heat energy value I2t of the fuse is greater than the energy of the circuit pulse, the fuse can withstand it. The "time-melting heat energy curve" is a tool to provide the designer with the ability to withstand the pulse when selecting the fuse (it can also be in the form of current-melting heat energy curve). Further, the fuse will suffer certain damage even if it does not fuse under the pulse impact, in other words, the I2t of the fuse will be reduced at this time, That is, the ability to withstand pulse is reduced, so this attenuation factor must also be considered when selecting the fuse. Generally, a simple calculation requires a margin of 3-5 times to ensure that the fuse has sufficient impulse resistance. There is a contradiction between the impulse resistance of fuse and its protection performance. We must find a reasonable balance between these two aspects and find the best combination point. Select the type and specification of fuse with proper melting heat value and enlarge enough and reasonable safety margin to meet the carrying function (pulse resistance) of fuse.
