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10 2024-08

　　Difference between disposable fuses and self-healing fuses

　　1、 Structure

　　There are two types of self-healing fuses: polymer PPTC and ceramic CPTC. We usually use polymer self-healing fuses, which are composed of polymer resin and conductive particles distributed in it. Under normal operation, the polymer resin tightly binds with the conductive particles outside the crystal structure, forming a chain like conductive path. Under normal operation, the resistance of self-healing fuses is very low, ranging from tens of milliohms to several ohms.

　　A blown fuse is composed of three parts: the main body, electrode terminals, and bracket. The main body is its core, which is a melt made of low melting point metal wire or metal sheet. The electrode terminals are used to connect the circuit and the melt, with good conductivity, and the support is used to fix the melt.

　　2、 Principle

　　For PPTC self-healing fuses, during normal operation, the heat generated by the current flowing through it is very small and will not change the crystal structure. When the circuit is short circuited or overloaded, the heat generated by high current will melt the polymer resin and expand the matrix, thereby separating the carbon black particles and forming Trip elements. After troubleshooting and cooling the crystallization again, the carbon black particles form conductive channels again, restoring low resistance. Specifically, the principle of self recovering fuses is energy balance.

　　As for the blown fuse, when the current is overloaded or short circuited, the heat generated is greater than the heat dissipation, and the heat gradually accumulates on the melt. Once the temperature rises to the melting point of the fuse, the fuse melts and the current is cut off. After troubleshooting, it cannot be restored.

　　3、 Performance parameters

　　There are many differences between blown fuses and PPTC self recovering fuses in terms of internal resistance, action time, safety performance, and self recovery.