What is the function of a fuse? What are the components? What can it be used for?

Fuse. Widely used in power systems.

It is used as a protective device in various electrical equipment and household appliances. A fuse is an electrical appliance that melts the melt and disconnects the circuit with the heat generated by itself when the current exceeds the specified value. The fuse melts the melt according to the heat generated by itself after the current exceeds the specified value for a period of time, so that the circuit is disconnected; A kind of current protector made by using this principle.

The fuse is mainly composed of three parts: the melt, the melt pipe and the melt seat.

1. Melt. The melt is often filamentous, sheet and grid-shaped, which is the main component of the fuse, and can be divided into a melt without thermal inertia, a melt with large thermal inertia and a melt with small thermal inertia according to the size of the thermal inertia of the melt.

Melt heating time constant without thermal inertia.

It is small, melts quickly, and is generally a small spherical melt welded with a fusible alloy (such as tin or cadmium alloy) on top of a filamentous copper or silver melt; The heat generation time constant of the melt with large thermal inertia is very large, and the melting is very slow, and it is generally a melt made of lead as the main material.

The melting velocity of a melt with small thermal inertia is between the above two, and it is generally a melt made of zinc as the main material. The fusing current of the melt is generally the rated current.

one to two times.

Second, the melt pipe. A melt pipe is the outer shell of the melt and is made of heat-resistant insulating material.

It can be filled with melt of different current levels, but the rated current of the melt can not be greater than the rated current value of the melt. The so-called rated current of the melt pipe refers to the current value determined by the allowable temperature rise of the melt pipe for long-term operation.

3. Melt seat. The function of the melt seat is to fix the melt pipe and the external lead-out wire. When a fuse is connected to a circuit, the melt is connected in series in the circuit and the load current flows through the melt.

When a short circuit or overcurrent occurs in the circuit, the current passing through the melt heats it up; When the melting temperature of the melt metal is reached, it will fuse by itself, and during the arc burning and arc extinguishing process, the fault circuit will be cut off to play a protective role.

The function of the fuse is to protect the line and its equipment from the damage caused by short circuit faults!

Commonly used fuses**.

Generally, the fuse is composed of a fuse core and a container base.

The fuse core is the main part of the fuse, which can be selected according to the actual power of the electrical equipment used!

Fuse base, which varies depending on the fuse. It is used to connect the wiring of the protected electrical equipment!

A fuse refers to a kind of protection device that blows the melt and disconnects the circuit with the heat generated by itself when the current exceeds the specified value. The fuse is usually made of lead-tin alloy, zinc, copper, and other materials with low melting point, and is widely used in high and low voltage power distribution systems and control systems, as well as electrical equipment.

Fuse. The main features are:Overcurrent protection mainly plays a role in protecting the safe operation of the circuit. It is widely used in power distribution systems and control systems, mainly for short-circuit protection or severe overload protection.

When the short circuit, the current in the circuit is the largest at this time, and this current value must undoubtedly far exceed the rated current of the equipment.

Therefore, in order to cut off the circuit in time to protect the equipment from damage, the fuse is used as an element, the principle of which is that a large current can be generated in the circuit at the moment, and the fuse fuse is quickly blown before the equipment is not damaged, so as to achieve the purpose of cutting off the circuit.

The principle of fuse selection

1. Select the model of the fuse according to the circuit requirements and installation conditions. For circuits with small capacities, semi-enclosed or non-filler-free enclosed are selected; The choice of large short-circuit current includes packing closed type; Semiconductor component protection selects fast fuses.

2. Select the rated current of the fuse according to the load characteristics.

3. The selection of all levels of melt needs to cooperate with each other, the latter stage should be smaller than the previous stage, the current on the main gate and each branch line is different, and the selection of fuses is also different.

4. Select the rated voltage of the fuse according to the line voltage.

5. The protection melt current of the AC asynchronous motor should not be too small (it is recommended to double the rated current of the motor). If the choice is too small, it is easy to cause the motor to burn out after the one-phase fuse is blown out, and the thermal relay must be matched for overload protection.

The role of the fuse in the circuit is overcurrent protection, which can also be called short-circuit protection.

When the short circuit, the current in the circuit is the largest at this time, this current value is undoubtedly far more than the rated current of the equipment, if the circuit is not cut off in time at this time, then soon the electrical equipment will be burned out because of the high current, so in order to cut off the circuit in time to protect the equipment from damage, the fuse is used, the principle is that it can produce a large current in the circuit instantly, and the fuse fuse is quickly blown before the equipment is not damaged, so as to achieve the purpose of cutting off the circuit.