The PPTC self recovery fuse is a typical positive temperature coefficient thermistor, and the self generated resistance increases with increasing temperature. In practical applications, engineers often ask about the resistance value of PPTC components after action. The following figure shows the relationship curve between the recovery time and resistance of PPTC components after action.
This figure illustrates that even after a few hours, the resistance of the PPTC component is still greater than the initial resistance. After a long period of time, the resistance of PPTC components will continue to decrease and eventually approach the initial resistance; Due to the possibility that the recovery time may be several days, months, or years, it is unrealistic to expect the resistance of the PPTC component to recover to its initial value after action. Therefore, when selecting PPTC components, R1max should also be considered when determining the operating current Ihold, where R1max is the upper limit resistance value of the PPTC component after one hour of operation.