The role of the fuse

Fuse is a kind of electrical component used to protect the safety of the circuit. When a circuit malfunction or abnormality occurs, it is accompanied by a rising current, and the rising current may damage some important or valuable devices in the circuit, and may also burn the circuit or even cause a fire. If the circuit is correctly placed in the fuse, then the fuse will be in the current abnormally high to a certain height and a certain time, its own melting cut off the current, so as to play a role in protecting the safe operation of the circuit. Therefore, the function of a fuse is to automatically cut off the power supply when the current in the circuit exceeds a set value, preventing overloading, short-circuiting, malfunctioning and equipment damage.

The working principle of fuses

The working principle of the fuse is based on thermal and electromagnetic effects, when the current passes through the fuse, the heat generated is able to make the fuse in the melting point rise, when the current exceeds a certain threshold, the fuse will quickly blow, cut off the circuit.

When the current flows through the conductor, because there is a certain resistance of the conductor, so the conductor will heat up. And the amount of heat follows the formula: Q = 0.24I2RT; where Q is the amount of heat, 0.24 is a constant, I is the current flowing through the conductor, R is the resistance of the conductor, T is the time of the current flowing through the conductor; according to this formula, we are not difficult to see the simple principle of the work of the fuse. Once the material used to make the fuse and its shape have been determined, its resistance, R, is relatively well established. As current flows through it, it heats up, and the amount of heat generated increases with time. The magnitude of the current and resistance determines the rate at which heat is generated, and the construction of the fuse and the condition in which it is mounted determines the rate at which the heat is dissipated.

When operating normally in a circuit, the heat generated by the current through a fuse is not sufficient to bring the melting point to the thermal fuse. The fuse is maintained in a stable condition and normal operating current can pass through it. When an overload or short-circuit condition occurs in a circuit, the current increases dramatically and the heat generated exceeds the fuse’s ability to withstand it. At this point, the temperature inside the fuse rises and reaches the melting point. Once the melting point is reached, the fuse breaks, cutting off the circuit and therefore stopping excessive current from flowing through the circuit and equipment. This prevents the circuit from being damaged, catching fire or putting personal safety at risk. Once a fuse has blown, it needs to be replaced with a new one to restore power to the circuit. Fuses are usually designed to be disposable, as their conductive function can no longer be restored after they are disconnected.

Fuse selection should be based on the current rating, voltage and melting time of the circuit. The current rating is the value of current that the fuse can continuously pass, above which the fuse will blow, and the voltage should generally be less than or equal to the operating voltage of the circuit. The melting time is the time from the current exceeding the rated value to the melting of the fuse, usually determined by the material and design parameters of the fuse.