Product Property

Applied Principle

When the traditional fuse being used for overcurrent protection, it only can protect one time; once burned out it must be replaced. But the resettable fuse has a double functions: overcurrent protection and automatic reset.

Overcurrent protection JKPPTC element is in series with the circuit, under nomal circumstances it presents low resistance to ensure the normal work of circuit: once the short circuit or other unusually high current happened, the self-heating of JKPPTC cause its impedance increase to prevent the current increase, So playing the role of protecting current.

Automatic reset- once the fault resulting in overcurrent being removed, JKPPTC element will automatically return to its low resistance state, with no need for replacement and keep away from the continuously circulating on-off state which can cause circuit damage. The JKPPTC resettable fuse's special structure determines their double functions. It is manufactured by mixing high polymer and conducting materials. Under normal circumstances, conducting materials forms a three-dimensional electric passage by the polymeric materials which keep the JKPPTC's resistance low. In case of passing unusually high current, JKPPTC element's temperature will rapidly rise, cause the polymer materials expand, then the conducting passage break, the impedance rapidly rise and the passing current turn low, the circuit like break off to protect itself. When the high current disappearing, the self-heating of JKPPTC will be not enough to keep it in high resistance state, so its impedance will turn to low resistance state. Compared to the traditional fuse, JKPPTC has the advantages of resettable, smaller and stronger.

Operating principle

 The operating principle of JKPPTC Resettable Fuse is based on the dynamic equilibrium of energy. The curren passing JKPPTC component will cause some heat, part or all the heat diffuse in the air, while the stay heat can rise the temperature of JKPPTC component.(show in the under diagram)
1. Under normal working,the dynamic equilibrium of energy keep the JKPPTC’s temperature and resistance low. (T<25 ℃)
2. When the current or the environment temperature rising, but the heat produced and that sent forth still reach a equilibratory state, The JKPPTC will still in low resistance. (R<Rc,T<25℃)
3. When the JKPPTC’s temperature increaces to Tc,If the current and ambient temperature continue to further rise, then the stay heat will be larger and larger, thus causing the temperature of JKTTPC component abruptly rising. In this stage(Tc), the least change of temperature will cause resistance value substantially increasing, and JKPPTC component will be in the high resistance protection state(Rc~Rp,Tc~Tp). The increase of impedance will prevent current from rising ,and the current will rapidly fall in a little time,thus protecting circuit units from damage.
4. If the heat produced by the applied voltage is enough to the diffusing by the JKPPTC component , the component will remain in the operating state (high resistance).Once the applied voltage disappears, JKPPTC will automatically reset itself.

Characteristics of Restring Time

Within some seconds after the current disappearing, the temperature of JKPPTC component will drop soon and it will rapidly reset itself into the low resistance state.

Environment

1. Increase of ambient temperature over 20°C will cause current passing the resettable fuse dropping swiftly.
2. When ambient temperature being at 20°C, 100 % of current on the line will pass through the resettable fuse, but if there are still so much current as over doubling the rated value produced, the resettable fuse will operate.
3. The higher the ambient temperature, the larger the passing current and the shorter the operating time. The reduction rate of ambient temperature and current value is shown as following table: