This section provides overview, applications, and principles of resettable fuses. Also, please take a look at the list of 15 resettable fuse manufacturers and their company rankings.
A resettable fuse is an electronic component that can serve as a fuse to prevent overcurrents and has the advantage of being able to be used repeatedly. It is also called a polyswitch or polifuse.
A PTC thermistor is made of conductive polymer and differs from a fuse in basic principle. In a fuse, an overcurrent causes the fuse to blow, which also breaks the circuit. In a resettable fuse, an overcurrent causes the temperature inside the element to rise, increasing the resistance and limiting the current.
Resettable fuses are used to protect circuits with repetitive overcurrents. They are also used in high-density mounting to intentionally short circuits, since a fuse would completely stop the circuit. Since they are smaller in size than fuses, they save space and have the advantage of being resistant to shock and vibration because their structure is not easily broken.
These advantages are utilized in motors, switching power supplies, satellite receivers, fire alarms, electric carpets, communication devices such as smartphones and tablets, computers, etc.
A resettable fuse consists of a conductive polymer with metal electrode foils on both sides, which are clipped together. Lead wires are soldered or welded to connect to the electrode foil. This is the same structure as a PTC thermistor, which has the property of increasing resistance as the current increases.
Conductive polymers consist of conductive particles such as carbon or nickel dispersed in an insulating polymer. Resistance can be adjusted by varying the amount and material.
The higher temperature inside a resettable fuse due to overcurrent causes the resistance to increase, thereby limiting the current. Unlike a fuse, a resettable fuse does not break the circuit, and the current flow returns to normal when the internal temperature drops. Therefore, they can be used repeatedly.
The property of a resettable fuse is that its resistance value increases rapidly when the magnitude of the current exceeds a certain value and the temperature changes. This is due to the melting of the conductive polymer. The reactivity may be low for minute increases in current.
*Including some distributors, etc.
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