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PTC Resettable Fuse Working Principle
Its core material consists of high-molecular polymer (plastic) blended with conductive carbon black particles. Under normal operating conditions, carbon black particles connect with one another to form conductive paths with ultra-low resistance. When overheating occurs, the polymer matrix expands physically, breaking these conductive channels and triggering an immediate sharp surge in resistance to cut off the circuit current.
Normal Working State Resistance remains extremely low (ranging from several milliohms to several ohms), exerting negligible impact on circuit normal operation.
Overcurrent & Overheating Fault State Temperature rises sharply → Polymer expands → Device switches to high-impedance state → Current is restricted to an extremely tiny value, equivalent to an open circuit.
Power Off & Cooling Recovery Once the fault source is removed and the device cools down, the polymer shrinks back to its original size. The internal conductive channels are restored, and the circuit automatically resumes normal conduction.
Core Characteristic: Self-resetting Capability
This is the most prominent distinction from conventional disposable fuses. Standard fuses operate on a one-time mechanism—once blown, they must be replaced. In contrast, resettable fuses feature reusable protection performance; after fault elimination, they can automatically recover and provide circuit protection repeatedly.
