Current flow in a conductor always generates heat. Excess heat is damaging to electrical components. Overcurrent protection devices are used to protect conductors from excessive current flow. Thus protective devices are designed to keep the flow of current in a circuit at a safe level to prevent the circuit conductors from overheating.
A fuse is a one-time over-current protection device employing a fusible link that melts (blows) after the current exceeds a certain level for a certain length of time. Typically, a wire or chemical compound breaks the circuit when the current exceeds the rated value. A fuse interrupts excessive current so that further damage by overheating or fire is prevented. Wiring regulations often define a maximum fuse current rating for particular circuits. Overcurrent protection devices are essential in electrical systems to limit threats to human life and property damage. Fuses are selected to allow passage of normal current and of excessive current only for short periods.
Polyfuse is a resettable fuse that doesnâ€™t need to be replaced like the conventional fuse. Many manufacturers also call it PolySwitch or MultiFuse. Polyfuse are designed and made of PPTC material in thin chip form. It is placed in series to protect a circuit. Polyfuse provide over-current protection and automatic restoration.
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