Resettable fuse, is a kind of overcurrent electronic protection components, the use of polymer organic polymers under high pressure, high temperature, vulcanisation reaction conditions, doped with conductive particles of material, after a special process and become. Traditional fuse overcurrent protection, can only protect once, burned out need to be replaced, while the self-recovery fuse with overcurrent and overheating protection, automatic recovery of dual-function.

Working Principle

The self-recovery fuse is composed of specially treated Polymer and Carbon Black distributed inside.

Under normal operation, the polymerised resin closely binds the conductive particles outside the crystalline structure, constituting a chain-like conductive electrical pathway, at this time the self-recovery fuse is a low-resistance state (a), the line current flowing through the self-recovery fuse generates a small amount of thermal energy, will not change the crystal structure.

When a short circuit or overload occurs in the line, the large current flowing through the self-recovery fuse, the heat generated by the polymerised resin melts, the volume grows rapidly, forming a high-resistance state (b), the operating current decreases rapidly, thus restricting and protecting the circuit.

When the fault is removed, the self-recovery fuse re-cooling crystallisation, volume contraction, the conductive particles to re-form the conductive path, the self-recovery fuse is restored to a low-resistance state, thus completing the protection of the circuit, without manual replacement.

Operation Principle

The action principle of the self-recovery fuse is a dynamic balance of energy, the current flowing through the self-recovery fuse, due to the relationship between the thermal effect of the current, produce a certain degree of heat (self-recovery fuse are resistance), the heat generated by all or part of the heat emitted to the environment, and did not emit heat will increase the self-recovery fuse element temperature.

During normal operation, the temperature is low and the heat generated is balanced by the heat dissipated.

The resettable fuse element is in a low resistance state and the resettable fuse does not operate. When the current flowing through the resettable fuse element increases or the ambient temperature rises, the resettable fuse remains inoperative if the balance between the heat generated and the heat dissipated is reached. When the current or ambient temperature increases again, the resettable fuse 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 emitted, resulting in a sudden increase in the temperature of the self-resettable fuse element. At this stage, a small temperature change can cause a large increase in resistance. At this point the self-resetting fuse element is in a state of high resistance protection. The increase in impedance limits the current, which drops dramatically in a very short period of time, thus protecting the circuit equipment from damage. As long as the heat generated by the applied voltage is sufficient to dissipate the heat from the self-recovery fuse element, the self-recovery fuse element in the changed state can remain in the operational state (high resistance).

When the applied voltage disappears, the self-recovery fuse will be restored automatically.