Slow fuses are also called delay fuses. Their delay characteristics show that the circuit remains intact when non-fault pulse current occurs and can provide protection against overload for a long time. In some circuits, the current at the moment of switching is several times greater than the normal operating current. Although the peak value of this current is very high, it appears for a short time. We call it impulse current, and we also call it impulse current or surge current. Ordinary fuse is not able to withstand this current, such a circuit if the use of ordinary fuse is afraid it can not be turned on normally, if the use of larger specifications of fuse, so when the circuit overload and can not be protected. The melt of the delay fuse is specially processed. It has the function of absorbing energy. Adjusting the amount of energy absorption can make it resist the impulse current and provide protection against overload. The delay characteristics are specified in the standard. If the specified characteristics of the standard cannot meet your requirements, you can contact the manufacturer for a solution.