Self recovery fuse is a kind of electronic components of over-current protection, the use of macromolecular polymer in high pressure, high temperature, curing reaction under the condition of mixed conductive particle materials, after special processing and. The traditional fuse overcurrent protection, can only protect once, burn off the need to be replaced, and since the restoration of the fuse with a thermal protection, automatic recovery of dual function.

Working principle of self restoring fuse
Self recovery fuse consists of a specially treated polymer resin (Polymer) and a conductive particle (Black Carbon) distributed in it. Under normal circumstances, the polymeric resin tightly conductive particles bound in the crystalline structure, form a chain conductive path, self recovery fuse is a low resistance state, through the heat generated from the current recovery fuse is small, does not change the crystal structure.
When short-circuit or overload, since the current flows through the heat recovery fuse will make the polymer resin melt volume rapid growth, the formation of high resistance state, the working current decreases rapidly, and thus restrict and protect the circuit. When the fault is eliminated, the self recovery fuse re cooling crystallization, the volume shrinkage, conductive particles to form a conductive path to restore the state of low resistance, no artificial replacement. Self recovery fuse classification
Self recovery fuse according to the material can be divided into polymer and ceramic PPTC CPTC two, according to the package can be divided into lead ins and SMD patch, can also according to the voltage divided into 600V, 250V, 130V, 120V, 72V, 60V, 30V, 24V, 16V, 6V etc..
The main advantages of polymer PPTC are: the normal temperature and zero power resistance can be very small, large current products only a few ohm, the power consumption is small, can be neglected, the volume is relatively small. Can be connected in series in the circuit for the vulnerability of over-current protection, temperature fuse, resistance mutation speed, in MS, heat capacity is small, short recovery time, impact resistance, can be recycled up to 8000 times as much protection. PTC can be used as a temperature fuse, to achieve the dual protection function of over current protection and over temperature protection.
The main advantage of CPTC ceramic is easy to manufacture, the price is cheap, but the resistance is high, large volume, large loss in road, there are tens of thousands to omega range, suitable for small current over-current protection, negative resistance effect, prone to high temperature overheating (resistance smaller), protection is slow, in hundreds of MS magnitude and the large heat capacity, long recovery time, the application scope is relatively narrow, can not be applied to the rapid protection circuit, wire harness protection, PCB line protection, more and more used in the heating device, in some small signal circuit, does not need to consider the loss of place can be selected.

Over current protection of self recovery fuse in UNO Arduion
UNO Arduino can be directly powered by USB port. The yellow part of the picture is the insurance tube, when the current of the UNO is greater than 500mA, the insurance tube will be automatically disconnected to prevent damage to the computer. Insurance tube with self recovery function, when the UNO 5V required to restore the Arduino to allow the scope, the insurance will automatically restore the connection, continue to provide UNO 5V Arduino voltage.

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　　Main technical parameters of self recovery fuse

　　How long recovery from the restoration of the fuse? How much is the response rate of the self recovery fuse?