Fuse is a circuit protection device

When the current exceeds a specified value, it will melt itself, thus breaking the circuit. As a protection device against short circuits and overcurrents, the fuse is one of the most commonly used protection devices.

Principle of operation

It utilizes a metal conductor as a fuse connected in series in the circuit, when the overload or short-circuit current passes through the fuse, it melts due to its own heat, thus breaking the circuit. Fuse structure is simple, easy to use, widely used in electric power systems, various electrical equipment and household appliances as a protective device.

Common types

Insertion fuse: It is commonly used in 380V and the following voltage level at the end of the line, as a distribution branch line or short circuit protection of electrical equipment.
Spiral fuse: There is a fuse indicator on the upper end of the fuse, once the fuse is melted, the indicator will pop up immediately for the user to observe. It is commonly used in machine tool electrical control equipment. Its breaking current is large, can be used for voltage level 500V and below, current level 200A below the circuit for short-circuit protection.

Enclosed fuse:

Enclosed fuse is divided into two kinds of filler fuse and no filler fuse. Filled fuse is generally a square ceramic tube, filled with quartz sand and melt, strong breaking capacity, for the voltage level of 500V or less, the current level of 1KA or less in the circuit. Fillerless closed type fuse will fuse into the closed cylinder, breaking capacity is slightly smaller, used for 500V, 600A below the power grid or power distribution equipment.

Fast Acting Fuses:

Fast Acting fuses are mainly used for short circuit protection of semiconductor rectifier elements or rectifier devices. As the overload capacity of semiconductor components is very low, can only withstand a large overload current in a very short period of time, so the short-circuit protection is required to have the ability to fuse quickly. Fast blow fuse is characterized by fast melting speed, high rated current, strong breaking capacity, stable current limiting characteristics, small size.

Self-returning fuse:

Uses sodium metal as the fuse, which has high conductivity at room temperature. When a short-circuit fault occurs in the circuit, the short-circuit current generates high temperature so that the sodium is vaporized rapidly, and the sodium in vapor state shows high resistance state, thus limiting the short-circuit current. When the short-circuit current disappears, the temperature drops, the sodium metal to restore the original good conductivity. Self-returning fuse can only limit the short-circuit current, can not really break the circuit. The advantage is that it is not necessary to replace the fuse, can be reused.