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A self-resetting fuse is an overcurrent electronic protection component that is manufactured through a special processing technique, using high-molecular organic polymers to which conductive particle materials are added under conditions of high pressure, high temperature, and vulcanization reaction. What are the standard requirements regarding the technology of self-resetting fuses? 1. PPTC thermistors with a rated zero-power resistance should be packaged in categories corresponding to this zero-power resistance value, and the resistance range should be indicated on the outer packaging. After the voltage and current resistance tests, the coefficient of variation in resistance for each group of samples, δ|Ri after – Ri before / Ri before – (Rj after – Rj before) / Rj before |, must be ≤100%. 2. The PTC effect refers to the property where a material exhibits a PTC (Positive Temperature Coefficient) effect, meaning that its resistance increases as the temperature rises. Most metal materials exhibit the PTC effect. In these materials, the PTC effect is manifested as a linear increase in resistance as the temperature rises, which is what is commonly referred to as the linear PTC effect. 3. The nonlinear PTC effect refers to the phenomenon in materials that have undergone a phase transition, where their resistance increases sharply by several to a dozen orders of magnitude within a narrow temperature range. A fairly wide range of conductive polymers exhibit this effect, such as polymer PTC thermistors. These conductive polymers are very useful for manufacturing overcurrent protection devices. 4. The initial resistance Rmin is the resistance value of the polymer PTC thermistor in the self-resetting fuse series, measured at an ambient temperature of 25°C before it is installed in the circuit. 5. At room temperature, Rmax applies to the operation of self-resetting fuse series polymer PTC thermistors or during reflow soldering. The resistance value measured one hour after installation on the circuit board. 6. Resistance (Rmin)/Resistance (Rmax): At a specified ambient temperature, such as 25°C, the resistance value of specific models of self-resetting fuse series polymer thermistors before they are installed in a circuit lies within a defined range, that is, between the values (Rmin) and (Rmax). This value is listed in the resistance field of the specification sheet. 7. Holding current Ihold: The holding current is the current that can pass through a self-resetting fuse series polymer PTC thermistor while it remains in its non-activated state. Under specified environmental conditions, the device can remain in this state for an infinite period of time without transitioning from a low-resistance state to a high-resistance state. 8. Operating current Itrip: the steady-state current that causes the polymer thermistor in the self-resetting fuse series to operate within a specified time under defined environmental conditions.