plug in mcb for old fuse box.Working principle of self recovery fuse

　　The polymer overcurrent protection element is made of polymer materials with conductive particles added. The basic principle is an energy balance: when the current flows through the component, heat is generated due to the power consumption of the current, and some of the generated heat is dispersed and sent to the environment, while others increase the temperature of the polymer material. At the corresponding working current, the heat generated by the component and the heat dissipated reach a balance, and the current can pass through normally. When excessive current is generated, the component rapidly generates heat that cannot be dissipated in a timely manner, resulting in an increase in the temperature of the polymer material inside the component. When the temperature reaches the crystallization and melting temperature of the material, the polymer material rapidly expands, blocking the conductive path composed of conductive particles, resulting in a rapid increase in electrical resistance (see figure), limiting the passage of large current and thus providing overcurrent protection. After troubleshooting, the PTC cools and crystallizes again, causing volume shrinkage and the conductive particles to form a conductive path again. The self resetting fuse returns to a low resistance state, thus completing the protection of the circuit without the need for manual replacement.

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