1.　The operating principle of our PTC resettable fuse is based on the dynamic equilibrium of energy, with part of or all the head brought about by the current passing PTC component due to the relation with PTC sending forth into the ambience while the heat not sending out raising the temperature of PTC component. Temperature is rather Iow during normally working, while a dynamic equilibrium between the heat produced the that sent forth being reached. When PTC component being at Iow resistance state, PTC does not operate. And though the current passing PTC component increases and the ambient temperature rises, but if the heat produced and that sent forth reaching a equilibratory state, PTC will still not operate. When current and ambient temperature further raising, PTC will come to a rather high temperature. If right now current and ambient temperature continue to further rise, then the quantity of heat produced will be larger than that sent forth, thus causing the temperature of PTC component abruptly rising. In this stage, the least change of temperature will cause resistance value substantially increasing and PTC component will be in the high resistance protection state. The increase of impedance will limit current, which will dramatically fall within a very short time, thus protecting circuit unit from damage. So provided for the quantity of heat produced by the applied voltage is enough to match that sent forth by PTC component, the PTC component under changing state will always remain in the operating state (high resistance) Once the applied voltage disappears, PTC will automatically reset itself.

2.PTC series type definition:

3.PTC parameter symbol Definition： 　

　Ih---------Hold current：maximum current at which the device will not trip at 20ºC still air.
　It---------Tripping current:minimum current at which the device will trip at 20ºC under specified
　　　　　 condition.
　Pd-------Typical power dissipation: Typical amount of power dissipated by the device when in tripped
　　　　　 state air environment.
　Vmax----Maximum device operating voltage.
　Imax-----Maximum fault current device can withstand without damage at rated voltage.
　Rmin( Rmax) ------Minimum（Maximum） device resistance at 20ºC prior to tripping.
　Time-to-Trip------- Maximum time to trip at specified current.(generally at 5Ih)