快速熔断器分断能力的选择

　　快速熔断器的外壳强度在很大程度上确定了对最大故障电流的分断能力。其次，快速熔断器内部的金属熔片形状、填料吸附金属蒸汽能力和热量、熔断体的电动力等都影响分断能力。设计整流器时应计算“整流变压器”的相间短路电流，并按此电流选用具有足够分断能力的快速熔断器。分断能力不足的快速熔断器会持续燃弧直至爆炸，严重时会导致交直流短路，故额定分断能力是一个安全指标。
　　另外，产品制造的分散性也是影响分断能力的因素之一。
　　易于忽视的问题是在短路故障时线路的功率因数，因为在快速熔断器分断时所产生的电弧能量的大小与电路感抗的大小有很大的关系，当线路功率因数cosφ＜0.2时对分断能力有特别高的要求。
　　快速熔断器分断时的能量Wo=Wa+Wr+W1
　　式中：Wa---电弧能量；Wr---电阻消耗能量；W1---线路电感释放的能量。
　　在分断能力满足“整流器”的要求时，还要注意分断瞬间电弧电压峰值（标准中称为“暂态恢复电压”）不能过高，要在快速熔断器制造时予以限制，使其低于半导体器件所能承受的最大值，否则半导体器件将会损坏。故分断时间最短的熔断器不一定最适用。
　　当快速熔断器用于直流电路中时，因为在直流分断过程中不存在电压的过零点，这对快速熔断器的可靠分断是一个苛刻的条件，所以一般情况下快速熔断器若用在直流电路中只能用到快速熔断器额定电压的60%，最好选用直流快速熔断器。

Shell strength fast fuse largely determines the maximum fault current breaking capacity . Secondly , fast fuse inside the molten metal sheet shape , filler metal vapor adsorption capacity and heat , electric power and so affect the fuse body breaking capacity . Design rectifiers calculating " rectifier transformer " in phase short circuit current and the current selection here has sufficient breaking capacity for rapid fuses. Insufficient breaking capacity fuses fast will continue until arcing explosion can cause serious AC and DC short circuit , the rated breaking capacity is a safety indicator.
In addition, the dispersion of manufacturing is one of the factors affecting breaking capacity .
The problem is easy to overlook short-circuit fault lines in the power factor , because the size of the fuse in the fast breaking arc energy generated by the size of the circuit inductance of a great relationship , when the line power factor cosφ <0.2 when breaking the ability to have a particularly high demands.
Energy Wo when breaking fast fuse = Wa + Wr + W1
Where : Wa --- arc energy ; Wr --- resistance energy consumption ; energy W1 --- line inductance release .
When breaking capacity to meet the " rectifier " requirements, but also pay attention to breaking peak instantaneous arc voltage (standard called " transient recovery voltage" ) is not too high , should be restricted in the fast fuse manufacturing, to below the semiconductor devices can withstand maximum, otherwise it will damage the semiconductor devices . Therefore, breaking the shortest fuse necessarily the most appropriate .
When fast fuse for DC circuit, because there is no DC voltage zero crossing breaking process , which is reliable breaking fast fuse is a demanding conditions, so under normal circumstances with a quick fuse if the DC circuit fast Fuse only use 60% ​​of rated voltage , the best selection of DC fast fuses.