When traditional fuse being used for overcurrent protection, it only can protect one time; once being blown out it must be replaced. But the resettable fuse as a new-type overcurrent protection element has the double functions of overcurrent protection and automatic reset.

Overcurrent protection JKPPTC element is serially connected to the circuit, under normal circumstances it presents low resistance state and can ensure the normal work of circuit: in case of occurring short circuit or unusually high current, the self-heating of JKPPTC may make its impedance increasing to limit current very low, so playing the role for protecting current.

Automatic reset-once the fault resulting in overcurrent being removed, JKPPTC element will automatically return to its low resistance state, which not only avoid maintenance or replacement but also avoid continuously circulating switching state which can cause circuit damage. The reason for JKPPTC resettable fuse having the double functions of overcurrent protection and automatic reset lies in its special structure. JKPPTC resettable fuse is manufactured by mixing high polymer with conducting materials. Under normal circumstances, conducting materials through polymeric materials forms three-dimensional passage, and JKPPTC's resistance value is very low. In case of passing unusually high current, JKPPTC element's temperature will rapidly rise, and accordingly polymer materials will expand, and lead to conducting passage breaking, thus resulting in impedance dramatically rising, the passing current turning low and circuit being like break off, so achieving the goal of protection. When unusually high current disappears, the self-heating of JKPPTC will be now enough to maintain its high resistance state, so its impedance will turn to low resistance state. Compared to the traditional fuse, JKPPTC possesses the advantages of resettable, little volume and solidness.