Littelfuse Fuseology

　　保險絲是一種溫度敏感器件，用作電路中的故意薄弱環節（圖1）。當過載或短路發生過流時，它會中斷電路。過電流條件使熔絲金屬元件熔化，從而打開電路并保護下游電路。過載是一種過電流事件，它被限制在正常電流路徑上。當電流超過導線或設備額定值時發生過載。這可能發生在太多的設備連接到電路，或者當一個設備連接到電路故障的方式，使其提請高于正常電流，通常在一到六倍的正常電流范圍內。持續過載最終過熱電路元件。因此，保險絲必須打開電路經歷持續過載損壞之前發生。

　　A short-circuit event occurs when current flows out of its normal path. It occurs when an accident or malfunction creates an unintended path for the electricity to flow from the power source to ground. This shorter， more direct path to ground bypasses the resistance normally offered by the wiring and devices connected to the circuit. With virtually no resistance left to impede current flow， the voltage forces higher and higher current to flow through the wires to the point of the short-circuit. Under such a condition， the current will quickly build to such a high level that the heat generated can cause insulation to burn and equipment to be damaged unless the circuit is opened through the use of a fuse.