保险丝(以下简称保险丝)由聚合物树脂基体及分布在里面的导电粒子组成，在正常情况下，导电粒子在树脂基体中构成链状导电通路，保险丝表现为低阻抗（a）。电路中有过电流发生时，流经保险丝的大电流产生的热量使聚合物树脂基体体积膨胀，切断了导电粒子形成的链状导电通路，导致保险丝的阻抗迅速升高，从而起到对电路的过流保护作用（b）。故障排除后，树脂重新冷却结晶，体积收缩，导电粒子重新形成导电通路，保险丝恢复为低阻抗。自恢复保险丝原理

自恢复保险丝参数

D2920P250TF       在自恢复保险丝选型过程中，主要涉及以下参数

1. 保持电流（Ih）：25℃静止空气环境中不触发电阻突越的最高电流。
2. 触发电流（It）：25℃静止空气环境中PTC聚合物自复保险丝从低阻转为高阻抗的最小电流。
3. 最大电压（Vmax）：PTC聚合物自复保险丝的最大工作电压。
4. 最大电流（Imax）：PTC聚合物自复保险丝能承受的最大电流。
5. 动作功率（Pdtyp.）：25℃环境温度时PTC聚合物自复保险丝动作状态下的消耗功率。
6. 动作时间（Ttrip）：5倍保持电流下最大动作时间。

SMD0805P010TF      SMD0805P020TF       SMD0805P035TF      SMD0805P050TF
SMD0805P075TF      SMD0805P100TF       SMD1206P012TF      SMD1206P016TF
SMD1206P020TF/24   SMD1206P025TF       SMD1206P035TF/16    SMD1206P050TF
SMD1206P050TF/15   SMD1206P075TF       SMD1206P075TF/13.2  SMD1206P100TF
SMD1206P110TF      SMD1206P150TF       SMD1026P200TF       SMD1210P005TF
SMD1210P010TF      SMD1210P020TF       SMD1210P035TF       SMD1210P050TF   

SMD1210P075TF      SMD1210P110TF       SMD1210P150TF       SMD1812P010TF
SMD1812P014TF      SMD1812P020TF       SMD1812P050TF       SMD1812P075TF
SMD1812P075TF/24   SMD1812P075TF/33    SMD1812P110TF        SMD1812P110TF/16
SMD1812P110TF/24   SMD1812P110TF/33    SMD1812P125TF/16     SMD1812P125TF/6,4L
SMD1812P150TF/8    SMD1812P150TF/12    SMD1812P150TF/24     SMD1812P160TF/8(4L)
SMD1812P200TF      SMD1812P260TF       SMD1812P300TF       SMD2016P030TF
SMD2016P050TF      SMD2016P100TF       SMD2016P100TF/33    SMD2016P150TF
SMD2016P200TF      SMD2920P030TF       SMD2920P050TF       SMD2920P075TF
SMD2920P100TF      SMD2920P125TF       SMD2920P150TF       SMD2920P185TF
SMD2920P200TF      SMD2920P200TF/24    SMD2920P250TF     SMD2920P260TF
SMD2920P300TF      SMD2920P300TF/15