Selection steps for self-healing fuse PPTC.plug in mcb for old fuse box

　　The self-healing fuse PPTC is a type of overcurrent electronic protection component, which is made by adding conductive particle materials to a polymer organic polymer under high pressure, high temperature, and vulcanization reaction conditions, and processed through a special process. Self recovery fuse (PPTC: Polymer self recovery fuse) is a positive temperature coefficient polymer thermistor used for overcurrent protection and can replace current fuses. When the circuit is working normally, its resistance value is very small (voltage drop is very small). When the circuit experiences overcurrent and causes its temperature to rise, the resistance value sharply increases by several orders of magnitude, reducing the current in the circuit to below the safe value, thus protecting the subsequent circuit. After the overcurrent disappears, it automatically returns to a low resistance value. The above is the working principle of a self recovery fuse.

　　Chip self recovery fuse

　　Most people are already familiar with the selection steps for self restoring fuses, but not everyone is familiar with them. Below are a few points summarized by fuse manufacturers, hoping to be helpful to you.

　　(1) Determine the maximum ambient temperature, working current, working voltage, protection current, action time, and other parameters for the normal operation of the protected circuit.

　　(2) Select suitable device packaging based on PCB space and processing conditions.

　　(3) Select a product series with a withstand voltage level greater than or equal to the maximum working voltage based on the maximum working voltage.

　　(4) Based on the maximum ambient temperature of the circuit (greater than 25 ℃) and the working current in the circuit, compare the temperature reduction rate of the self recovery fuse to select the suitable product specification for I-hold current.

　　(5) Determine whether the required action protection time is met based on the action time curve of the self recovery fuse of this model.

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