What is a fuse?

Fuses, commonly known as insurance, are the simplest and most commonly used protective appliances in low-voltage power distribution systems and motor control circuits. When used, it is connected in series with the circuit and installed vertically on each phase line. When the circuit or equipment is overloaded or short-circuited, the current in the circuit exceeds the specified value, and the heat generated by itself will fuse the fuse link, thereby disconnecting the circuit. It can avoid equipment failure expansion and burning. It can also avoid accidents such as fire caused by equipment short circuit.

Note: It is not allowed to install a fuse link holder on the neutral line (zero line) of the two-phase three-wire and three-phase four-wire main circuit, because the circuit will be charged after the neutral line is broken, which may easily cause personal electric shock. The open circuit of the main supply zero line may easily cause the user voltage to rise and damage the electrical equipment.

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Structure and composition

The fuse link is mainly composed of three parts: the melt, the fuse tube for installing the melt, and the fuse seat.

1. The melt is also commonly known as the fuse link, and the melt is generally made of pure metal or alloy conductive material, which is the most critical component of the fuse. The material, size and shape of the melt determines the characteristics of the fuse.

2. The melting tube is made of heat-resistant insulating materials such as glass, ceramics, etc. It is used to fill the melt and has an arc-extinguishing effect when the melt is blown. The melt and the fusion pipe are integrated, and the melt is inside the fusion pipe, so the melt cannot be seen, and the installation and replacement are regarded as a whole.

3. The fuse seat is made of insulating and flame-retardant materials, and its function is to fix the fuse tube and the external lead wire (terminal). There are indicator lights on some fuse base shells, and the lights are on after the melt protection is blown. In fact, resistors and diodes are connected in parallel at both ends of the fuse. When the fuse is in good condition, the indicator light is short-circuited and the indicator light is off, which can quickly determine whether the fuse is good or bad.