We introduce the over-current maintenance application of polymer PTC resettable fuse:
1.PTC effect Say that a kind of data has PTC (Positive Temperature Coefficient) effect, that is, positive temperature coefficient effect, which only means that the resistance of this data will be added as the temperature increases. For example, most metal materials have PTC effect. In these guesses, the PTC effect shows that the resistance increases linearly with temperature, which is generally called the linear PTC effect.
2. Non-linear PTC effect The data after the phase transition will show the phenomenon that the resistance is rapidly added several to dozens of orders of magnitude along the narrow temperature range, that is, the non-linear PTC effect. Quite a variety of types of conductive polymers show this effect, such as polymer PTC resettable fuses. These conductive polymers are very useful for manufacturing overcurrent maintenance devices.
3. Since the polymer PTC self-recovery fuse has a unique positive temperature coefficient resistance characteristic, that is, PTC characteristic, it is extremely suitable as an overcurrent maintenance device. The application method of the self-recovery fuse is the same as the general fuse, which is used in series in the circuit.
When the circuit is working normally, the temperature of the self-recovery fuse is close to room temperature, and the resistance is very small. The series connection in the circuit will not hinder the current flow; and when the circuit is overcurrent due to the fault, the temperature of the self-recovery fuse will increase due to the addition of heating power When the temperature exceeds the switch temperature, the resistance will increase sharply in an instant, and the current in the loop quickly decreases to a safe value. After the action of the self-recovery fuse, the current in the circuit has dropped significantly, and t is the action time of the self-recovery fuse. Because the polymer PTC self-recovery fuse has good programmability, its sensitivity to temperature can be adjusted by changing its own switching temperature (Ts), so it can perform both over-temperature maintenance and over-current maintenance.
The polymer PTC resettable fuse is a direct-heating, step-type resettable fuse. Its resistance change process is related to its own heat and heat dissipation. Therefore, its holding current (Ihold), operating current (Itrip) and operating time are affected by Influence of ambient temperature. The relationship between the typical maintenance current and operating current of the resettable fuse and the ambient temperature: when the ambient temperature and current are in zone A, the resettable fuse will operate when the heating power is greater than the cooling power; when the ambient temperature and current are in zone B, the heating power is less than For heat dissipation power, the self-recovery fuse will be in a non-operating state for a long time; when the ambient temperature and current are in zone C, the heat dissipation power of the self-recovery fuse is close to the heating power, so it may or may not operate.