The case strength of a fast-acting fuse largely determines the breaking capacity for the maximum fault current. Secondly, the shape of the metal frit inside the fast-acting fuse, the ability of the filler to absorb metal vapor and heat, and the electromotive force of the fuse all affect the breaking capacity. A fast-acting fuse with insufficient breaking capacity will continue to arc until it explodes, and in severe cases it will cause an AC-DC short circuit, so the rated breaking capacity is a safety indicator.
In addition, the dispersion of product manufacturing is also one of the factors that affect the breaking capacity.
The problem that is easy to ignore is the power factor of the line when the short circuit fault occurs, because the arc energy generated when the fast-acting fuse is broken has a great relationship with the size of the circuit inductance. When the line power factor cosφ<0.2 Capabilities are particularly demanding. Energy Wo=Wa+Wr+W1 when the fast-acting fuse breaks；In the formula: Wa --- arc energy; Wr --- energy consumed by resistance; W1 --- energy released by line inductance.
When the breaking capacity meets the requirements of the "rectifier", it is also necessary to pay attention to the peak value of the arc voltage at the moment of breaking (called "transient recovery voltage" in the standard) not too high. The maximum value that the device can withstand, otherwise the semiconductor device will be damaged. Therefore, the fuse with the shortest breaking time may not be the most suitable.
When the fast-acting fuse is used in a DC circuit, because there is no voltage zero-crossing point during the DC breaking process, this is a harsh condition for the reliable breaking of the fast-acting fuse, so in general, if the fast-acting fuse is used in a DC circuit Only 60% of the rated voltage of the fast-acting fuse can be used, and it is best to use a DC fast-acting fuse.