What is the Main Function of Self-Recovery Fuses?
1. The structural principle of self-recovery fuse:
Self-recovery fuses are PTC thermal elements with positive temperature coefficient. It is made up of a polymer, a conductive material, etc., which is connected in series in the circuit to replace the conventional fuse. Figure 17-9 shows the appearance of a self-recovery fuse.
The self-recovery fuse is in the on state when the circuit is operating normally. When an overcurrent fault occurs in the circuit, the temperature of the fuse itself will rise rapidly, and the polymer material will quickly enter a high-resistance state after being heated, and the conductor will become an insulator, cutting off the current in the circuit and bringing the circuit into a protection state. When the fault disappears and the self-recovery fuse cools, it is in a low-resistance conduction state, and the circuit is automatically turned on.
The operating speed of the self-recovery fuse is related to the magnitude of the abnormal current and the ambient temperature. The higher the current and the higher the temperature, the faster the operating speed.
2. Common self-recovery fuses Self-recovery fuses have plug-in, surface mount, chip and other structural shapes.
Commonly used plug-in self-recovery fuses are RGE series, RXE series, RUE series, RUSR series, etc., used in computers and general electrical appliances. Table 17-2 shows the main parameters of the RXE series and RUE series self-recovery fuses.