Working principle of self recovery safety tube.littelfuse smd fuse

　　The operating principle of a self restoring fuse tube is a dynamic balance of energy. The current flowing through the components of the self restoring fuse tube series generates heat due to the relationship between the self restoring fuse tube series. The heat generated is completely or partially dissipated into the environment, while the heat not dissipated will increase the temperature of the components of the self restoring fuse tube series. The temperature during normal operation is relatively low, and the heat generated and dissipated reaches a balance. The self-healing fuse series components are in a low resistance state, and the self-healing fuse series does not operate. When the current flowing through the self-healing fuse series components increases or the ambient temperature increases, but if the balance between the generated heat and the emitted heat is reached, the self-healing fuse series still does not operate.

　　When the current or ambient temperature increases again, the self-healing fuse series will reach a higher temperature. If the current or ambient temperature continues to increase at this point, the heat generated will be greater than the heat dissipated, causing a sudden increase in the temperature of the self-healing fuse series components. At this stage, a small temperature change will cause a significant increase in resistance. At this point, the self-healing fuse series components are in a high resistance protection state, and the increase in impedance limits the current. The current drops sharply in a short period of time, thus protecting circuit equipment from damage, As long as the heat generated by the applied voltage is sufficient for the heat emitted by the self-healing fuse series components, the self-healing fuse series components in a changing state can remain in operation (high resistance). When the applied voltage disappears, the self recovery fuse can automatically recover.

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