PPTC (Polymer Positive Temperature Coefficient), that is, the positive temperature coefficient thermistor of the polymer. As shown in Figure 1, the PPTC self recovery fuse is made up of polymer matrix material and conductive particles. When the abnormal current through the PPTC self recovery fuse, the heat generated (I2R) the polymer base material expands, conductive particles in the polymer matrix material package can separate to cut off the PPTC self recovery fuse conductive channel makes PPTC resettable fuse resistance increased, thereby reducing the abnormal current. When the abnormal overcurrent fault is cleared, the PPTC self recovery fuse polymer matrix material shrinks to the original shape, re connects the conductive particles, the conductive channel will recover, and the PPTC self recovery fuse resistance will return to the original low resistance state. The above process can be circulate many times.
Figure 2 is the curve of the resistance of PPTC with the temperature change. It can also be seen from the diagram that the resistance of the PPTC self recovery fuse will increase with the increase of temperature. The internal temperature of PPTC self recovery fuse is determined by the current size flowing through the PPTC self recovery fuse. Therefore, we can also call PPTC self recovery fuse a sensitive device for temperature and current.
The biggest feature of PPTC self recovery fuse is that within its rated application range, PPTC self recovery fuse does not need to be replaced after each troubleshooting. It can be repeatedly applied to the circuit, saving time and cost effectively.