Littelfuse Fuseology

　　Littelfuse Fuseology

　　保险丝是一种温度敏感器件，用作电路中的故意薄弱环节（图1）。当过载或短路发生过流时，它会中断电路。过电流条件使熔丝金属元件熔化，从而打开电路并保护下游电路。过载是一种过电流事件，它被限制在正常电流路径上。当电流超过导线或设备额定值时发生过载。这可能发生在太多的设备连接到电路，或者当一个设备连接到电路故障的方式，使其提请高于正常电流，通常在一到六倍的正常电流范围内。持续过载最终过热电路元件。因此，保险丝必须打开电路经历持续过载损坏之前发生。

　　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.